I cut the liner with an oscillating saw, took awhile but if you're careful you can get a clean cut all the way around. I also cut along the seams where the floor banks along the engine compartment, that way you can fit the liner out of the companionway. I would build your floor flush to the edges of the piece of the tub you cut out and just re-install (sans nasty verm). Look at marks blog
http://j30hull62.blogspot.com/, it was really helpful to me.
