Just do what I saw a couple years ago, good sized jet boat and trailer loaded in the back in the pickup, RV trailer on the back.

"I had a 12' flat trailer i used for my quads and towed behind my 79 chev stepside. It was titled and plated as required by law in oregon. So yeah must have plates."

I went to the DMV when I bought my pickup bed trailer. They told me that as long as the trailer will haul less than 1200 lbs it does not need plated or titled.