I can't remember -- did you buy a Fusion? And if so, did you get the Sitech neck ring? That can significantly impact arm mobility.
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4th Element underwear is some of the least bulky stuff on the market.
More than likely, your drysuit is binding somewhere
agreed with PfcAJ, pre stretch your suit on the surface with extra gas.
Close your valve on the surface and add gas to your suit, go in a head down position so the gas goes to your feet. Then lay prone on the surface and grab your forearm, pulling the drysuit material towards your wrist. Open your vent and get ready to dive. This should allow you to have a lot more mobility.
GC