I want to install standard hatch covers in the bulkheads. The cut outs are 6 1/2 inches in diameter but the standard hatch covers are 6 inches in diameter. Are the flages of the standard hatch covers large enought to provide attachment and a good seal?
Have you looked at deck hatches?
BECKSON MARINEScrew-In ABS Plastic Deck Plates, Non-Skid Diamond Cross-Cut Pattern
The cutout size is 6-1/2" and the flange is 8-1/8".