Attaching Hatch Holders

[VERSO I]

I've just bought a pre-aged boat and have many many projects I'd like to do. The hatches (all Lewmar, I think) on the boat all have basic hinges, none have the creaky friction hatch levers I'm used to. I've ordered a medium-sized spring hatch holder for each from Moonlight Marine (Moonlite Marine - Hatch Holders), but I haven't been able to handle them yet. To support the two ends of the holders, I'm anticipating that I'll need to install screws into the base aluminum hatch frames and some type of fastener through or onto the plexiglass lenses. The lenses are original 1988s and look the part, with plenty of crazing.

My questions:
What material will I encounter when I pilot drill through the aluminum frames (bedded in the deck)? Do I need to apply sealant to screws entering that material? How long should they be? Other thoughts?

How should I attach the top of the spring to the plexiglass lenses? Ideally the solution wouldn't leave anything pointy or obnoxious on the outside of the lens, and of course shouldn't weaken it or create a leak. Assuming I need to drill through the lens, any tips on making sure I don't crack them? Could I just pilot drill part way through and then thread a hot screw into them, maybe with some sealant for strength?

Thanks!