I take off all the stuff that cat trailer have mounted on them for the boats and get it down to a bare frame. Then I get two 4x8x3/4 marine plywood. Heavily paint them to insure against rotting, then screw them onto the frame.
On some trailers the fenders are higher than the frame. In this case you have to use 2x2 on top of the frame, then screw to the 2x2s.
Finally, go to your local carpet store (ours is best on Friday) and go to their dumpster and grab a bunch of used carpet and either glue it or tack it down.
If I am moving a boat locally, I lower the mast and let it cradle between the rudder blade and the tiller arm, move it forward so the bob is not sticking out too far, and tie the mast. That keeps the rudder from wobbling and wearing out parts, and secures the mast.
Then, upon getting to the beach, just scoot the mast aft, slip it onto the mast base ball and raise it. You are ready to sail.
When we go longer distances, we usually take at least two boats and often three.
If two, I have 2x4 carpeted pieces and simply load one on top of the other. Bottom one needs to take off the rudders, but upper the rudders stay on.
I never take the masts apart. Usually just put them on the 2x4s under the top boat and tie them to the wood.
If three boats, I load the first one upside down on the edge of the trailer, the next one nests into that one on the other side of the trailer, and then load the top boat as if only two boats. Best to load the two topped boats to the left side of the trailer (the high side of the crown in the road.)
Rick