Have you considered using displacement to get the thickness? If you plug a pure colour into the displacement channel it should displace everything equally...

In my experience, double sided cloth is a b*tch to work with when it comes to dynamics, but since displacement is calculated at render time, it MAY work. 

So far I've only used displacement for details like buttons ect on dynamic clothes because those are so tricky to do what with the welding and all, but at least theoretically it should be possible to add a general thickness to something with displacement.

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  Using Poser since 2002. Currently at Version 11.1 - Win 10.