Cockpit Tray Surgery on Ocean Kayak Prowler Big Game

I'd like to get bilge access on my Ocean Kayak Big Game for both storage and safety.  As it is I can't reach a place to use a bilge pump.  I considered the square hatch OC sells for this model but I do believe my butt is big enough to cover it up  when I'm sitting on the kayak.  Plus I don't think it's the right size to let me get rods into it.

So I'm looking at that cockpit tray which as factory configured has a minimal amount of semi-dry space covered by a sloppily fitting lid.  I'd like to begin by cutting the bottom out of the cockpit tray.  Then later I'd like to create one of those fiberglass hatch covers.

Can anyone see a big red flag on this play?  Has anyone else done it or seen it done?  Advice, thoughts, hysterical laughter?

Below is a diagram of the Big Game for reference.

Once upon a time there was a feller named Steelhdr that roamed the halls here. He did exactly what you are proposing. He never did the fiberglass mod, but the plastic lid did just fine for him.