Hey all. I am more familiar with doing static model kits (i.e., once they're done, NOTHING moves on them,) and so I've used testors orange putty for years. Only recently, I began to realize this was a ridiculously bad idea for Transformers; I used it on the RID Grapple I did and the damn thing's filled areas are starting to crumble apart. What type of filler material should/could I use to fill in gaps in between styrene for kitbashes? I need something that would be functional enough to undergo the movements of transforming, obviously. What do you guys use?