Here you have example of using dummy prop. You can see it as a red stick in the right part of chest. It is made with ball. Parented to chest and added to collision list. Before rendering material should be set transparent and prop will be invisible.

Converting clothes with dynamic room is easy if you use "one-piece" clothes. Before you try convert convert clothes with separate parts (for example belt, straps, ties etc) try something easier. It helps you understand what happend if something is going wrong.

BTW I've used Ishiro conforming shirt. Loaded obj welding identical verticles and calculated dynamic.

Ref your image you can place it on external host (messyshare or imagevenue) and send us link .
Ref WW - It is expensive but all PhilC softwares are worth theirs prices.