Question about cut out for rear hatch

[OCD]

I'm building with 1/4" baltic birch ply which I intend to hang wider than my sides to attach trim to. I'm thinking I should also double up on the hatch skin along the outer edges to give me a more secure base to attach the side trim. I'm planning on using the Hurricane hinge with zero offset, should I undercut the hatch area by 1/2" to accommodate this or do I need a little extra depth? Also, how do I determine how far up the roof line the hatch/hinge should be?

Thanks

[Moho]

Here's how I am doing it, the seal is a 1/2" thick seal and shown compressed in the diagram. Mine is a woody, not sure if you plan a woody or aluminum trim

[jonw]

I'm building with 1/4" baltic birch ply which I intend to hang wider than my sides to attach trim to. I'm thinking I should also double up on the hatch skin along the outer edges to give me a more secure base to attach the side trim. I'm planning on using the Hurricane hinge with zero offset, should I undercut the hatch area by 1/2" to accommodate this or do I need a little extra depth? Also, how do I determine how far up the roof line the hatch/hinge should be?

Thanks

I used 1/4in ply for my hatch base (under the aluminum) and a 1/4in undercut worked fine for me. I wouldn't undercut it any more than 3/8, to allow for slop and weatherstripping.