Before you use a hole saw, consider a plunge router. The access plate needs to be flush with the floor, necessitating a recess, a lip to which the plate is fastened, and then an access hole. I removed the baseplate from my plunge router and fabricated an exaggerated egg shape plate out of 1/4" plywood. I drilled a 1" hole for the bit and two two pilot holes in the plate for a pivot screw. I was installing an 8" plate so the first pilot hole was the radius from the center to the outside of a 3/8" straight router bit. I set the depth of the cut equal to the thickness of the plate - about 1/8" - and it created an absolutely perfect 3/8" wide recess. The second hole decreased the radius 3/8" and that cut resulted in a 3/4" wide recess. I then switched to a 1/4" straight bit and made several passes, lowering the bit each time. The teak ply floor is about a 1/2" thick, followed by a thin layer of fiberglass, a honeycomb composite about 1" thick, and another layer of glass. I did that cut by lowering the bit in increments, and (important!) kept a shop vac hose next to the router to capture the sawdust and fiberglass dust.
Sounds complicated but it worked perfectly. I have pics but have never learned how to post. If you're interested send me an e-mail address and I'll send them to you.
Sanford
ADAGIO, '09 R25