ok here is a possible solution. Do exactly what you did by making it dynamic, but make it have
no collision. Then create a model that has the collision you desire (or just use the original) and assign it a single texture that is see through, effectively making it invisible and place it within the dynamic model in the editor. So now you have 2 models-
1. a model that has no collision but all your textures, and
2. a non dynamic model placed inside it with a single invisible texture that has the desired collision.
Hope that helps!
Model pack 66-99 high quality items...cheap!!
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