I actually found the remains of the hatch I pulled out. It would drop into a cutout 9 5/8ths square. My recollection is that the bomar was the only hatch that came close enough to the size of our cutout to drop in.
You do need to be careful with the bedding compound. Silicone works. Someone re-sealed the plexiglass in ours with the wrong stuff and it degraded both the plexiglass and the plastic of the hatch. However, it did take at least 10 years after that mistake, before my foredeck was able to put his foot through it.
Tom
