Only silicone will stick properly to silicone but super glue like Zap-a-Gap will work. Otherwise create a rough surface for the silicone to bind to on the underside of the resin pieces and use more of the Ecoflex as the adhesive.
Thank you all for your suggestions. I did a test with some aquarium grade silicone and it seems that it will work pretty darn good. and alot cheaper than what Smooth-on was suggesting. Cheers!
Yes I have been, I've been super busy at work and haven't been able to update in awhile. I've ran into some problems with my first pull, I think i made it overly complex with what i was trying to do. If i can't salvage it I'll do a simpler cast.