I have added photos of raising the floor on our C 25. The border base is from 2 x 3's, the horizontal boards are 1 inch (real world 3/4") pine, doubled (screwed and glued). No holes in the hull floor. All construction lumber from Menard's. 2x3's instead of 2x4's to save weight and is sufficient. Can all be removed quite easily if another owner would prefer. Port doors adjacent to the floor I made anew, saving the originals for reversing the installation. It was not difficult after having spent some time figuring out a simple way to do it, taking into consideration of adding as little weight as reasonably possible. To make entering the forward V berth easily, I remove the last two boards for the night. To access the kitchen (or other area) any two boards can be removed and placed sideways to step down and, if desired sit on the sideways placed boards. I fill much of the area with Walmart plastic bins. The advantages besides the over 7' long storage space is the level area from from the first step into the cabin thru to the V berth and a much easier step up to the seats and a better height for the kitchen countertop for my wife. At just over 5'10" I have never bumped my head on the ceiling. If taller it would make sense to have the floor lower than the maximum I used dictated by the lower edge of the refrigerator. A fun and inexpensive simple project.