I used Vaclav's method for building hatch lips. To add the magnet here is what I did:
1 drew locations of magnets on hatches
2 Used shelf paper as release mold
3 Added first layer of bias cut glass and epoxy
4 Embedded 3/8" magnets in epoxy at the locations previously marked
5 Built the remainder of gasket channel and lip as per Vaclav's method.

Next I used a 1/2" forstner bit to cut holes in hatches to insert corresponding magnets. By tracing the locations on the hatch ahead of time I thought alighnment would not be a problem. Added 2 drops of epoxy to holes and popped the magnets in.

Results:

Hatches sat 1/16" proud of deck. I blame this on relying only on duct tape to support the hatches during the "sandbag process" of keeping the hatch lip in contact with the boat will epoxy cures. I think the duct tape sagged a little. So when I cut the holes in the hatches for the magnets I sunk them a little deeper than necessary. This allowed me to carve off some depth on the hatch so that it sits even with the deck.

Then I added a small piece of 4 oz glass and epoxy over the hatch magents to reduce scratching and rusting.

Also there is a bit of allignment problem especially noticable down the centre line of the deck. I think I can address this by adding a smidgeon of epoxy butter to one spot on the inside of the hatch lip. This would stop it from sliding off of alignment.

grant