I know that you asked Jack, but just for the record - my swim ladder, the same make but with four steps, mounts at the center rear of the swim platform, and there is plenty of room for the collapsed ladder to fold forward and lie flat on the swim platform. I have a line made fast to the bottom rung that allows me to pull it up from the cockpit.
I mounted mine using Rivnuts set in holes in the swim platform. It seems to be plenty strong, and during one of the Florida hurricanes the ladder beat a piling to death without suffering any real damage. I like to use the long-reach rivnuts with a fender washer beneath the platform, all gooped up.
1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida