it looks like you used thin, flat bar for the strut? That may not be the best choice for that application, since that shape is better suited for tension loads and you're putting it in a compression load situation. You really should use tube or box or round bar.
Decided to rake it out, its a bit of a dodgy way to do it but its efective?
I also found this tank and fender that look alright
I would take the pie section out of the backbone, so the force was compressing onto itself, and the bottom tube was intact and full strength. If I did cut the down tube like that I would grind away enough of the stamped part to get a good solid slug in that down tube, then drill and plug weld it up before you covered with the sheet. (maybe you did do that?) that frame has little to no integrity with that down tube inside cut.
It looks good, but more importantly choppers need to work, and they work hard.
How many mounting points do you have on the rear fender?
it would be cool to weld mount a sissy bar, out off the rear of the frame you cut off. you could also Mount your rear fender to the sissy bar adding more strength.
thats badass man! I'v been dreaming of building a dirt bike frame! Iv been trying to get my hands on one of my brothers bulltaco frame but he wont come off it due to he knows what im going to do with it LOL but great job man that thing is badass! can you tag that for the road?