I'm with Fiddleback on this. Assuming (big assumption, but work with me) proper surface prep and the right adhesive the bond between your handle and blade can be stronger than the handle material itself. I don't use G-Flex but E-120HP has similar properties. I've yet to pop a scale off even when trying to under realistic conditions. No cryogenic immersions followed by hammers and chisels or using a small fine blade knife as a pry bar after a prolonged soak at 300 degrees.
What I do, which is a combination of various things learned here and from others, is drill my tangs liberally in addition to any pin and tube holes I intend to use. This not only lightens the tang but provides plenty of glue plugs going from scale to scale through the tang. I slightly countersink those holes. I then take a coarse stone bit in my dremel and run it at low all around the inside of the tang flats. By inside I mean leaving a border to allow for final shaping and to make sure the actual visible edge once the scales are in place is still straight and smooth. I'm pretty aggressive with this, I'm not just roughing up the surface, I'm leaving slight gouges that cover most of the surface area not already removed by holes. That is followed by fresh 36 grit sandpaper done by hand, but using a knuckle for firm pressure. I scuff it up quite a bit, if I had my own sandblaster this would be the place for it. After that I blow it off and then wipe it down with a clean rag and then a clean rag with unscented acetone. Before all this started I've made sure my pins are cut and ready (also scuffed up with fresh sandpaper, usually 60 or 80 grit) and the scales are prepared. I generally don't do any internal drilling on the scales but they get a few passes on fresh 36 grit on the granite block. I also make sure my holes are slightly counter sunk on the tang side. I use fairly over sized holes in the tang whenever possible, the pins are NOT locked in metal to metal. Not wobbling all over, but plenty of room for epoxy to fill in around the pin and the tang.
Actual glue up is with a little dab of epoxy around the end of the pins before they get put into one scale and tapped in place. I put them in from the tang side but mostly because that's the slightly countersunk side and it's easier. Then I coat the inner surface of the scale with a thin layer of epoxy, avoiding the pins for the most part still. The goal here isn't to slather it on, just enough that there's completely surface coverage and filling those grooves. I usually let the handle rest on the bench (wax paper is my friend here for easy cleanup) and set the blade down onto it. Then I fill all those holes with epoxy. I don't overflow them, but pretty much let it fill flush to the surface of the tang. Then some more on the pins, again, mostly around the ends, so it's sliding into the scales as they go together. I coat the other scale the same as I did the first and put it all together. I fit things snuggly enough in terms of pin holes on the scales that this usually requires a fair bit of tapping with a mallet, it's rare that I can do it by hand. Once the second scale is in place I check for positioning and any issues and start clamping. I use small C clamps with moderate force, basically no more than is needed to get the handle material to sit snug to the steel. If you do the epoxy right that's not a lot of tension, if it needs a lot to stay flush after squeezing out excess epoxy you've discovered why your handles are popping off later, they've got a lot of tension all on their own, even before you flex the steel. Once it's all settled with clamps I take another rag with some acetone and wipe down the excess epoxy at the ricasso. I tape pretty close to where the scales will line up, so there's just the small line of exposed steel along with the front face of the scales to clean. If I do it right there's usually almost no epoxy coming out there so it's not a problem to clean up. I try to not over do the epoxy near the front for just that reason. I want a good bond but squeezed out epoxy is just waste anyway.
Then I let it sit for at LEAST the suggested setup time. Generally I go 8 hours with E-120HP before I remove the clamps and if it's 12 or so, oh well. I try to give it nearly a full day before any additional work though. It may be set up, but it's not remotely cured and the bond is still relatively fragile. After this it's just shaping, which can be minor or major depending on how much handle shaping I did prior to glue up. I vary there. I am careful to not overheat the pins, I don't want them getting hot enough to effect the epoxy bond they have. With synthetics or stabilized materials I can dunk regularly just like I'm grinding on the blade. With natural wood or other materials that don't like getting wet at this stage I just have to be patient and careful.
All that said, I have made one knife with no pins using the exact same technique. No changes other than it simply had no holes drilled in the scales for mechanical fasteners of any kind. I pounded the hell out of that thing trying to get the scales to pop off during anything remotely realistic. Still firmly attached. I've given it to an out of service Marine with instructions to continue abusing it and to let me know what finally does the trick. He knows not to be gentle, and it's not a pretty handle that makes a person shy about being rough with it. Canvas micarta coarse ground to shape with ripples and grooves for grip. I used it as a hammer on stone and masonary in various ways, pry bar when there was no way the objects were moving, 3/16 cpm154 takes a lot of force to flex when it's that short, but it did, I flexed it from mid blade to pommel until my palm hurt from applying pressure there. I froze the thing in our zero degree chest freezer for a few days then did it again. No change other than finding out the micarta is more slippery in that condition than with liquid water. I know, should have been obvious but.... With the coarse sand finish it's actually grippier when wet, but frozen was a different animal.
I'm not saying you can't pop a straight epoxy bond. I'm not saying mechanical fasteners aren't stronger. I'm just saying that it MIGHT be aliens, errr, wait. What I mean is that if you do it right, proper adhesives WILL form extremely strong bonds that are more than sufficient for most purposes. The key is giving them the right conditions to form that bond and being realistic. I wouldn't suggest a pinless handle for a heavy use full tang knife. I also wouldn't suggest it for a thin steel knife that will flex a lot. On the other hand, we don't peen mosaic pins and we don't peen micarta/G10 pins and we don't get all paranoid about them. It's all about matching your techniques and materials to the task. If my goal was to put the handle on a machete headed for the amazon I'd probably use all my adhesive bonding tricks, including borrowing a sand blaster, along with corbies that had JB weld on the threads before assembly. Does that make my a hypocrite when it comes to other methods? I don't think so. Not any more than we require different safety measures in race cars than we do in passenger cars, much less children's bicycles. What is suitable and even overkill at 10mph in the driveway is not the same as what makes sense at 220mph with a dozen other cars bumping into you and where horrific crashes are basically expected.
