I deraked a frame years back around 27deg what's a modern bike rake ,
But it changed the look of it to much because the rest of the bike was standard just my taste.
The tt500 I race now I just left it near standard and pushed the forks up through the triples to make it turn a bit better .
All the usa flat track bikes run 19 inch fronts 26/27 deg rake for the right corner speed .
You can try diffrent off sett triples but if it's a early model Tt,xt500 76 77 models the triples will hit the tank on full lock , it's allways the way you fix one prob and make another.