I'm not real sure what you're asking Thomas, but what I do is this:
I first put layout fluid on the tang's profile, and then mark center lines just as I do before I grind the blade.
Then I hollow grind the meat out of the tang, trying to get close to my desired thickness.
Then I set up the grinder with the vertical platen (hardened D2). I use one of those blade grinding magnets to hold the tang with one hand, and hold onto the tip of the blade with the other hand.
With the tip up, I flatten out the tang. I hold the blade and ricasso area above the belt and only let the tang area touch the belt. These magnets really help me out in applying even pressure. Once I get it really close, I spray it with blue layout die again.
After it dries on, I hit it against the platen again really lightly. If you have any high or low spots they will show...and you just have to keep at it that way.
I used to bring the taper up to where the bottom of the bolster would start. That means you have to have a different angle on your scales to match up with your bolsters (dovetailed or not).
Also, I do a lot of bolsters with radius grinds in them and such which causes all kinds of headaches with the taper below the bolster...so to alleviate all of this I started tapering the tang right up to where the top of the bolster will be.
This allows the bolsters and scales to all be in the same linear plane.
Hope I made sense, and if I didn't even come close to answering your question I'll try again
Good luck,
Nick