Hi Lou, I installed a 4" deck plate in my rear bulkhead. I don't use it as an access hatch - I thread a lock through it. I took a look last night and the flange around mine is 1" wide; so that would add two inches to the total diameter. I epoxied it in. I cut the hole after the bulkhead was installed. I forget what I used - there are several options for close-quarters sawing... in a pinch you can use a small piece of hacksaw blade held in a vicegrip (be careful snapping that blade) to cut the opening. Best thing to do is wait for the hatch to arrive or pick one up at a local marine supplier.

I hope this helps.
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