Take as little off as possible - initially.
Take off only enough to be able to seal your mask to Your face - no more. Later You can take a bit more off. So what it if takes even 5 dives before You decide how much of the seal you want to remove for your comfort?
Diving here in Northern New England, I have seen it time and time again; People buy a new drysuit and proceed to cut too much out of the seals:
1) neck seal on suit
2) neck seal on hood (usually the biggest violation)
3) wrist seals
Remember - You can ALWAYS take more off later, but You CANNOT add it back after You cut it off.......
Approach this task as a surgeon would, not a butcher!
On a liveaboard trip to Cocos Island, Costa Rica, a diver decided to cut the neck seal down on her wetsuit because it was too high for comfort on the front of her neck (back zippered model). She quickly cut the seal almost completely out, only to find that the suit she cut wasn't even hers! I will never forget the look on the suit owner's face when she looked at her destroyed wetsuit. And we were 32 cruising hours away from the mainland.
Do it slowly and carefully! Good Luck!
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