I am beginning hatch construction on my latest boat and I will be using rare earth magnets. I have 1/8" x 1/2" round I plan to use placing about 10 pairs per hatch. I have some great flexible ply for rims and shims so I will end up with a flush hatch. I may also use carbon fiber to cover the magnet containing rims for cosmetic purposes. I expect to take great care to seal the mags in epoxy to avoid water damage. I am posting pics at heirloomkayak.com and if anybody has well intentioned advice or comments I would love to hear them.
My next major undertaking will be a skeg upgrade for existing boats.
Robert, visionary