: How many 3/8" magnets per hatch, Larry?

: Would a jump to 1/2" be a good idea?

There must be a happy medium between enough and way too much. I went with the 3/8 because of the with of the lip (3/4" ply) I put 10 pair on the forward hatch spaced somewhere between 3-4 inches.( I also put washers behind the magnets in the lip to increase the force on at least half of the pairs.) There is a 4mm spacer between the lip and the deck. With the gasket compressed enough to make the hatch flush with the deck, the hatch still popped off easy enough. Too easy. I could envision something banging around in there whilst upside down and knocking the hatch loose. The internal bungie thing is more for secondary security. On the aft hatch, time was an issue so I just bungied it up. I know Rob M. uses 1/2" and have read one of his posts detailing a wooden prybar he has to use to get it loose.
It is nice to let the hatch loose and not have to worry about it going anywhere. When I get the time I'll add some magnets to the rear hatch.

Possibly using a thinner spacer or no spacer at all to get the magnets closer to each other might help make it stronger.

Larry