Installing a new/old thermo and was wondering how much movement I should see from the largest to the smallest - without any spring force on the bellows? I am only seeing about a half an inch? The potential issue is when it is contracted - cold? Does not seem to get max movement out of the cooling flaps. Any experience here?

From full cold to full hot is not really that much.
You gain movement from mechanical advantage of the arm on the operating rod of the flappers.

That sounds about right. The collapsed bellows is as small as it gets, and the bellows frame limits the maximum size.