I like the bead idea and I am sure it works great, but would it not make more sense to put the bead on the edge of the lid, instead of the inside edge of the lip and then have the gasket on the inside edge of the lip on the deck. If it as watertight as you say it is, would it not help to keep water from getting near the magnets? I know, the magnets are sealed well under glass, etc. but this extra precaution might help in the event that the seal on the magnets was lost.

Basically, I see reversing the whole set up as having advantages.

I see more clearly what you suggest.

To make a flush hatch with the gasket on the outside edge of the deck lip would require a recess in the deck lip for the gasket to sit in.

This still puts the gasket in a high wear position and it can collect sand and debris. It also makes a natural reservoir for water to collect in. The recess created by the bead in the gasket becomes another water collector.

Aesthetically it sucks.

With the gasket on the hatch cover there are no recesses for water to collect in. And it looks good.

Water washing over the deck and hitting the hatch/deck joint opening has to climb the sides of the deck lip to reach the gasket and with drain slots cut into the lowest part of the deck hatch joint, water has an easy exit.

I see this as an advantage, that water will loose pressure as it has to travel further to reach the gasket, trying to squeeze past the magnet to magnet contact of the area of the deck lip, away from the hatch edge.

But please, do it your way.

Rob