http://www.betamotorsports.com/benchracing/index.html
I always thought that the halfshafts varied in length. After reading that article I measured a bunch of them and they were all the same. I did go through the hassle of figuring out how to shorten them. I was about to do that then I just decided screw it I'm going with CV's. I figured after all that hassle I might as well go to the smoother CV joint since I'm running so much neg camber.
I think after I had it all figured out I found a post from 2126 (I think) and he had successfully done what I was planning to do to shorten the shaft. Basically you have to disassemble it, cut about 1" off of the inner part of the shaft, then I was going to tack weld the end of the shaft back on, I think 2126 actually had it machined to accept the original snap ring, and reassemble.
I've got a picture of a disassembled shaft which might help you, but I can't upload pics for some odd reason. I found your email address on your website and emailed the pic.