Its an interesting thought, but, what would you do with the boat while you
are using the trailer, and if the boat is moored or slipped, would placing
a flat load on the supports maybe unbend them so they later would not match
up with the curvature of your hull to properly cradle it?
Maybe better to buy one of those cheap fold up utility trailers, than risk
damage or bending of your precious boat trailer for the purpose it was
specically designed--and which you primarily need it. Or there is always
uhaul for $14.95/day.