Having trouble keeping silicone mold inside plaster shell

Hi, I want to cast a seemless torso peice using another Smooth-On silicone (Dragon Skin 10). I want to cast in a certain way with the plaster hard shell upright with the silicone (Smooth-On Body Double) fused also upright inside the plaster, basically welded to the plaster. I've used silicone glue, Krazy Glue, Gorilla tape- nothing seems to work- the silicone is heavy and just folds in on itself. Is there anyway to get a really bond with silicone and plaster?







 

Obviously new at this and could you some direction, thank you in advance!