I removed the plywood subfloor with a long pry bar, circular saw and ratchet straps.
It was a messy operation.
first, I set the circular saw to the thickness of the rubber + plywood, then made a couple lengthwise cuts. From there I used the pry bar to wedge under the floor and pull it up a bit. Next, since I had some of the windows out, I wrapped the ratchet straps around some of the ribs and put the hooks on the lifted edge of the plywood. Then I walked along the ratchet straps and slowly tightened each one. This worked for most of the plywood pieces, except for some that were wet and nasty. They broke and I had to pry them up with the bar. Most of the nails that were holding the plywood down actually pulled through the plywood, not out of the metal. I had to go over the floor with the pry-bar and pull out the nails one-by-one.