agree with rryman and campgems.
i use the sullivan, its the one that works best and its easy to install

http://www3.towerhobbies.com/cgi-bin...?&I=LXFV46&P=7

the other setups are too delicate.
if its a small trainer like 50" wingspan maybe you can do without a tail wheel at all like a skid...
if its 5 pounds plane then i would go with the sullivan.
some pics of attached after market part, notice the plate the bracket is attached to.

Alex