in the fuel tank hatch...don't over think it
Put a 1" wide strip of 1/2" pvc trim board (pine will work) under the lip, along the length of the edges. Temporary hold in place with a couple dabs of plain old silicone. Pre-drill a pilot hole through the existing holes in fiberglass. Screws
from the top will pull everything tight.

Be sure to silicone the hatch to be watertight!

I used jack nuts on my rod holders to finally keep them in place. The screws were constantly stripping, and I know people here have tried all kinds of repairs including wood strips, starboard, fiberglass, epoxy etc. But the jack nut did the trick, it's made for thin brittle materials, it's invisible when assembled, and should I need to get to the area behind the rod holder they simply unscrew.

I got mine from a local supplier, but this is what I'm talking about:
http://www.rivetsinstock.com/rivet-n...jack-nuts.html

I'm guessing you could also use Nutserts for some applications, but I don't think they would work for thin fiberglass. They would probably split or crack the hold during installation. (But would be great for thin sheet metal and might work for fiberglass. I just don't know. Anyways, Harbor freight sells a nice kit at a reasonable price:
http://www.harborfreight.com/45-piec...-kit-1210.html

I agree with Skunk. I've been trying to wean myself of the habit of always doing the hi tech costly route and overthinking stuff when fixing up a boat. A lot of times the cheap and easy works as good or better and will last longer than you will.

I remove the tank hatch every spring, inspect, clean off old sealant and reseal with SiliconeII (gutter&roofing). No need for 3M 5200/4200.

You HAVE to seal that hatch unless you want a tank like jetblue319's

Skunk you just answered my next question about should I caulk Your the man I think I will got your way Don't over think it I like that

What's jet blue 319

I agree with Phatt ,,I once used a simple piece of treated 2x4 laid against the underside of the flange and pull it up tight with screws ,,,,Done

Yeah but the wood would rot and you would have to do it again, I don't want to do it again so I don't think the wood would be a good idea .

If you are going to check & reseal every year it really doesn't matter. You can use whatever scrap you have lying around