Rob
Forum Moderator

Rocky is really for lots of smaller particles so not one large one. 

6DOF can be used, but you need to add the wall contact checks: you're not permitted to actually make contact because it breaks the topology. Any shape is permitted but you'll need to extend the UDF to avoid and mimic the body contact. 

Another option is the macro particle model. That's sphere's only but otherwise potentially the simplest option.