Sealant use
This is a non-structural part that simply sits atop the coach house to give the hatch some protection. Using sealant all the way around might be a good idea; then, again, it's likely more a matter of choice, I would think. However, pay some attention to the screws. If they enter into the core -- and most likely your coach house is cored -- then you should like likely overdrill the holes, fill with West System epoxy and then drill holes for your screws so as not to let moisture into the core. I've seen this a zillion times and have no idea why folks don't pay attention to this because it's a way to avoid big problems in the future. Well, that's my bit, mate. Good luck.
