The basic problem with small trailers is they have very simple suspensions with no shock absorbers. If you take a trailer unladen down a rough road
too fast it will jump around. The spring rates have to be engineers so the weight of the load compresses the spring sufficiently. If the spring/wheel combination is too stiff the trailer could get airborn on bumps and shake the tar out ouf your boat(s).
Even the small 4 x 4 Harbor Freight trailer with the 12 inch wheels can be a bit stiff with 3 or 4 boats up.

: Been looking for a trailer for a while now and just got one. It's an older
: light weight boat trailer that should be a good base to build a kayak
: trailer on. I have been looking at the commercial trailers for ideas on
: how to build the racks. Just wondering if anyone had an clever ideas.

: Being a woodworker I would prefer to work with wood. But I may end up just
: having someone weld me up a tower to put on it.