Got a 2.5 mm "walking plate" aluminium and some bolts. Cut two plates to shape and fastened them with two bolts. The trailer is made so the rear lights swing to the side when the airplane (or boat) is carried.
For the tail wheel I just used the existing bow rest. Removed the rubber to buffer the bow, and inserted two poly-carbonate plates cut to shape. With those plates the tail wheel gear fits like a glow in between and is held secure against swaying to the sides, in the same manner as the bow buffer rubber when a boat is hauled.
With this mod I can simply exchange bow buffer with the plates and I can haul my boat or the Onex as I wish
The aircraft is fastened to the trailer using ropes through the tie down loops in each inner wing.