That's exactly what I did 5 years ago to my Pace turned bike trailer. When I got it the floor was a little spongy and springy. I just got 3/4 plywood and screwed it down to the current floor and chaulked around the edges. You may not even need 3/4, 1/2 may do the trick but I over kill lol....It is now tough as nails and no bounce at all to it. I carry a HD Ultra at 800 lbs and have towed it all over the country with no problems at all. Just be careful at the rear where the ramp folds up. You have to allow room for the door to fold in so cut it about an inch short at the rear. Believe me it is a pain to try and cut it off after you got it glued and screwed down lol lol........oh keep an eye on your bearings...on one trip I heard rattling from the rear and here some how the wheel came loose. I have no idea how the bearing keeper backed off and allowed the wheel to almost come off the spindle.