UV Master on clothes flattening both sides?

[treedee]

Newbie here… I’m trying to create a simple t-shirt from a model and get a UV map for it.
I created a base t-shirt by masking the model and extracting. I then went to UV Master and clicked “Work on Clone”. Next I hit “Unwrap” and then “Flatten”. Didn’t look good. I played around a bit and finally created the seams by polygroup. This worked pretty well except that it unwraps both the inside and the outside of the t-shirt… is that normal? Is it possible to select only the surface or is it best to stick with the inside and outside being unwrapped?

Edit: Thought I’d put a couple of images in to illustrate

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[dillster]

Your model looks to have thickness, which is why both sides are UV’d.

[treedee]

Yes I can see that… I’ve tried extracting with zero thickness but that doesn’t work either.
The tutorials I’ve found relating to this show the subtool without the inside but I’m unsure how to do that… I tried splitting the polygroups but that didn’t work either.
How do you extract to a new subtool with no thickness?

UPDATE: I tried running a Group Split again and this time it worked. I was able to select the outside group and flatten the UV successfully.