Looks fantastic mate, particularly the black bike with the flamed tank! Be aware though, that by removing the support rails you'll weaken the frame and ruin the handling, but the Chopper look is all about form over function, so who cares?
Just don't go chasing modern sports bikes through those canyon roads, or you'll be getting to know the local hospital staff on a personal basis, ha ha!
You could try bracing the frame by adding more steel to the backbone, or making a bracket to tie the cylinder head to the frame a la Harley Davidson, which will be a good thing, for sure. Good thing is the stock (but modified) OEM frame fits the engine much better than any of those goofy hardtail frames that were designed for Harleys, with a huge gap between the rear of the engine and the rear wheel, where the HD gearbox would normally go.
I've got a junker frame here that someone cut (badly) so I think I'll give it a go myself! Cheers, Terry.