You're on a good track. It does help to pretaper the limb area prior to gluing up a relfexed or recurved bow, plus you could use it to taper lams for trilams and such. I have an adjustable/hinged lam sled made of aluminum. It's the shizznit. I originally made it for grinding glass bow lams, but have used it a lot more for all wooden bows than I ever did for glass bows. Anyway, my point is, even with aluminum, I added two little braces on each side to eliminate any deflection as it went through the thickness sander. Something to keep in mind if you go the 'hinged' route. Hinged sleds are nice because they're made with two flat pieces. You don't have to try to create the perfect taper with masking tape, drill bits, etc, you just hinge two flat pieces and then can adjust to make any taper you will ever want.