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			I wouldn't double up.  The fiberglass will serve to strengthen the plywood. Then the hatch gets screwed down and caulked in place.  All of which makes it very sturdy.    Do you have the cuddy or the center console?
		 
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1996 -19' NV Flats  115 Mercury 4-stroke 
1983 -20' Wellcraft Center Console 250 XS
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