Back doors are done, except they need handles for opening and closing. You can see that I took everyone's suggestions regarding some vents in the doors:
I used 1" u-channel top and bottom, knowing that my 5/8" plywood would get a lot thicker with the vinyl channeling.
I used flat head screws and countersunk the holes in the track for the attachment to the floor, so that the screws do not interfere with the doors. It fits snug in the track, maybe a little too snug. Doors are a bit tough to open and close, but I think I'll put some kind of lubricant in the track. Not sure what yet, I need something that will not make a mess on the white vinyl.
Also I put 1/4" aluminum shims under the track:
This is to allow water to pass under the doors and to the bilge in the event that the boat takes on a big wave. Not sure what others have done, but this was my method.