I've sort of flat ground a few hollow ground knives, including my Native FRN plainrdge.
Here's how I do it.
I use a small, cheap, aluminum oxide sharpening stone. The stones measure around 4" x 1" x 1/4" thick. They're made in China or Taiwan. I buy these at dollar stores or bargain stores, $1.00 for a package of two. These stones are coarse, of low quality, and not good for regular sharpening. They are, however, usefull, by way of size and price, for this sort of shaping of a blade. A small stone of this size is more usefull than a larger one. A good quality stone is not necessary for this sort of procedure, and doing this sort of thing kind of would damage a good stone for regular sharpening. So use a cheap stone.
Then, using the aforementioned sharpening stone, I rub away on the primary grind line, the line where the hollow-grind starts. I use different surfaces of the stone, it depends, maybe a corner, or an edge, or one of the flat surfaces. It varies.
For lubrication I use water or saliva, not oil - too messy.
First, I like to smooth out the grind line, so that instead of a sharp demarcation between the hollow ground part of the blade and the full thickness part, there's a smooth, flowing transition between the two parts. Then, I just keep rubbing away at the blade, bringing the grind closer and closer to flat-ground. How close I bring the grind to flat-ground depends on my mood at the moment. On one knife, I made a real effort to make the grind pretty darn flat. On others, I'm satisfied to get the grind sort-of-flat, that is: not as flat as can be done but good enough for me for the time being because it's too much trouble to take it any further right now. In this case, instead of the sharp change that occurs at the primary grind line, from full thickness of blade to hollow grind, there's instead a gradual transition, sort of an area of convex grind. So you have, starting from the spine and going down to the edge, full thickness, then convex grind, then hollow grind, then the edge.
I don't do this grinding all at one sitting. It can take a fair bit of grinding to get to the final result. I'll do some to start, and then continue some other time, some other day, when I feel like it. I'm in no big hurry, usually. It might be weeks before I'm finished.
When I'm sure I'm finished and have ground the blade down as much as I intend to, I'll polish out the scratches using various grits of sandpaper or emory cloth. Maybe some buffing compound as well. I'm not too concerned about getting a really polished finish.
I done this sort of thing on my 440v Native, smoothing out the primary grind line but leaving the grind line at the swedge unchanged. I've also done it on ATS-34 blades. I'm pleased with the results and intend to do it on other knives when I get around to it.
As far as reshaping the blade of your Navigator into a hawkbill, that's something I don't know about. I guess you could, sort of, but it sounds like too much trouble to me. You could try adapting my method above to the task.
Good luck.
