Fly-n-Hi
If your using molybdenum magnets (which is what they look like) I'd not use two as they can be hard to get apart, as I'm sure you've seen, and I would expect them to damage the model over time. Check out using some metal like a paper clip to give it some room to move so you can get the grip to give but I'd do a bit of testing. I'd be tempted to use some shims to stop the hatch moving too.
Are you going to try and move something past the magnet? It will grab anything metal you know so it could be worth putting the magnet on the hatch as it may be easier that way too.
I've been working on my Herb Deeks kit which has a lot of sanding but as its resin I've spent my time in a mask otherwise I'd be coughing up something solid!!
Phil