clayton,
You could build your gear diff as per instructions and accidently drop some superglue in it. Spools seem to be popular and work at most tracks around Sydney. They certainly give more pull out of the corners. Just need to drive alittle bit differently.
I can tell you Col has been giving me a hard time at Penrith on Mon nights with one fitted in his mini. The thing accelerates very hard out of the corners, more so than a tight ball diff/tight gear diff.
Yes, it does put additional strain on the outdrives etc, but if you want to be competitive its a small cost. Something I will be trying in the very near future.
Regards,
Calvin.