Tim.
There are all sorts of "non traditional things you can do in sport 40. The Ringmaster will work fine. Do yourself a favor to make things simple. This is from the guy who invented (it's documented) the thingy that moves the leadout back on low throttle, Jeff Rein.
Get the Brodak on the bottom bellcrank (unless you are using 24 mh) and run the controls exterior. much-o simpler-o.
A hook can be made by a swing down wire that is pulled by rubber bands just let it drag on takeoff.....a tail skid hook would also work, but unlike the 15 size jobs the 40 is hard to get to hang so maybe a drop down hook might make landings easier.
Disgusted with it all, the Reinman gave me his sport 40 and if you send me a private message, I'll send you pictures. Other than that, do whatever Erick says.
Ken