The method I used (the hard way) was to build a removable tail wheel assembly. I made a 1/8th ply plate 6 1/2" X 3" X 1 3/4", cut a hole in it 6 5/16" by 1 3/4" X 1 11/16". I then drilled holes around it for mounting with counter sunk screws that screwed into inner Ny-rod which is thick CA'ed onto the fuse botom for a flush fit.
I mounted a bulkhead reinforced with gussets on this plate to mount the Robart tail wheel and after the assembly is installed in the fuse simply cover with Ultra Coat. The wheel is steered by cables and retracted and extened with a push rod, both of these servos are in the factory tray's intended for the tail servos.
Good luck.