I've been wondering the same thing. I'll be cutting hatches & building hatch lips over the next couple weeks and am still undecided about what hold-down method to use.

There's a new Lee Valley store opening up just down the road from me on Monday (I'm so excited ), so I thought I'd pick up a handful of the 1/2" and 3/8" magnets to play around a little before deciding. If I discover anything useful I'll report back.

: I'm curious to know if anyone has done any measurement or studies involving
: the magnet diameter, placement, number, and proximity to each other before
: and after gasket compression (gasket type) to provide a decent or optimum
: seal without needing a pry bar to remove them? Good or bad experiences?