Mike,

I have used the two-part silicone but not with the thixotropic additive. I don't know if the two-part silicone has good adhesive properties - many one-part formulations do not. Its typically very difficult to bond to cured silicone, although I believe there are adhesives particularly formulated for that. You should put mold release (PVA works well) on anything you don't want it to stick to, and prep the surface for bonding where you do want it to stick.

Sam