0 - The first I've heard of a rendering problem with it. Often, problems in Poser4 (sans-ProPack) are the result of a corrupt geometry resource (.rsr). Try deleting the .rsr and see if it still happens.
1 - ERC and IK chains do not play well together. IK was built in at first, then based on tests (both in-house and beta), IK was omitted.
2 - None of the reference material collected made a distinction on valve port location, nor did several divers (amateur - master) when asked.
3 - The model was constructed based on photos of divers wearing their gear. Many manufacturer and safety references were used.
4 - In order to properly conform the rig to the figure it was intended for, some things MUST be done in the mesh (not to mention the topological and proportional differences). Believe me, rigging the joints a second time was not fun.
5 - Much like #4, in order to conform correctly, certain things must be done to prep the figure. When conformed, the fins fit as they were intended.

post #3 - Simply put, its called ERC (cascading). In addition to the standard manipulation, are channels that allow upstream/downstream manipulation. targetGeom was used in place of valueParm so that poses could be saved that utilized the 'dummy' channels.

-Rob