I've sanded off a few pounds of draw weight, but never enough to significantly change the tiller.

It's real important to make the glass removal even throughout the working portion of the limb. I always use a sanding block and do the sanding by hand. You don't want to get on there with an orbital sander and go nuts.

I don't know it for fact, but I've heard tell you should never remove more than 1/3rd the thickness of the glass when you're sanding. Since BW doesn't use very thick glass anyway, I can understand why they pitched a fit when you told them about your project.

With your unorthodox grip style (which we've discussed before), I'd say you'd be better off to have a set of limbs custom made to accomodate you, rather than try to modify standard set.