I made a hatch cover out of mahogany (all the teak on my boat is gone and replaced with mahogany, which is prettier). I did not like how I fit it and am making another one. The one I made is a trapezoid and turned out really well, quality-wise, but the fit is a problem to adapt removable-pin hinges to. Also it will not go down its own hole, since I left the moulded-in fibreglass spigot intact. For racing and handling spinnakers it's vital to get it out of the way.
I will be chopping out the spigot and making a new one (alá the Cherubini 44-style 'hatch box') over the fall. It will be square, and cutting away the spigot makes a larger hole (about 27" x 27"). It is actually quite simple to make-- a box within a box. You finish the coaming (inside) 'box' first (use 1/2" stock), then fit the outside one (of 3/4" stock) to the deck, and right before you are ready to glue it down you slice the outside box on the tablesaw to separate into a lid and a base. Make the lid at least 2-1/2" high. Then you attach the lower, fitted portion to the deck like a mounting ring, using a trim strip around the perimeter underneath like a backing plate. This adds stiffness to the deck too. Next you fit and attach the inside ring/coaming to it, up to within 1/2" of the inside of the Lexan (room for a gasket inside the hatch lid). Lastly you trim off the coaming under the deck (I like it about 3/4" deeper than the underside of the deck, for looks). If you see the C-44 at Annapolis this season, look at the foredeck hatch, and you'll see this is how it's made.
The whole wood structure gets saturated in epoxy and varnished for a UV barrier (or, you could just paint it all with Brightside). Once it's bedded down I will paint the bottom deck color. The top will be 3/8" or the same 1/2" translucent white Lexan as the one I already made (looks good against varnished mahogany). It can have ribs in it for stiffness and room for a solar vent.
I am eager to get this done (first I need some good wood for this) and I'll try to get my site up and online which will have pictures.
In the meantime I reiterate my age-old request that if anyone has a reasonably intact fibreglass H25 or H27 hatch lid and will send it to me, I will mend it and make a mold from it to produce new parts. The guy who sends me his old hatch gets a new one free.