Cab-o-sil is not used to "thicken" resin, but to keep it from running. It's not a filler, nor intended to be. It makes your resin or glue thixotropic, that is, it won't run off a vertical surface.

Please see: http://www.eagerplastics.com/cab.htm

Not sure about "Ammicille"

For strength, though, you don't want to add a filler. If you're laminating wood-to-wood, just use a thin layer of resin. If you want to add strength, then add 1-2 oz. glass cloth between the layers. You could also use fiberglass flocking, mixed into the resin. That's basically chopped-up fiberglass cloth. The fibers are randomly oriented in the hardened mix and add a tremendous amount of strength in a lamination. Because you control how much flocking you put into the mix, you can also control the weight.