Yeah I have done a few over the years too. When I did it there was no such thing as a registered Right-off. But I always repaired them the right way so no dramas. I always made a quid out of the ones I did, but I also was careful in my selections. And usually bought stuff that I may have some common parts for. Couldn't be bothered any more, as the time doesnt justify the meagre margin you can make. I would still do it for the same reasons as you though, and that is to make a racer outta it.
I agree with what you say about no being able to fully exploit the capabilities of a bike if you are woried about scratching it.
I have an 05 636, that I take very conservatively around a racetrack. I always ride it with a few tenths in reserve on track, whereas my racer, I just keep getting faster till I fall off.
I would love to ba able to afford both a late model roadie and a late model racer, but the nI would have to sell my two dirt bikes, and maybe my racing go-kart.

But hey, If any one wants a KDX200 or a KLX400, i may talk.

"I hate to advocate drugs, alcohol, violence or insanity to anyone, but they've always worked for me" Hunter S. Thompson.
There are really only two questions in life. 1.Which way do i go? 2.What is the lap record?