They're an abomination that should never have come into being. You can use them for FT though (GP's and Worlds, not in NEFTA though).
UKAHFT and NEFTA Hunter put them into Open class. In fact I think someone once put in a podium finish with a TX200 SR in Open class at a UKA national. I seem to remember they had to shoot off against Paul Wilson for 2nd place. I could be wrong though.
Is John thinking of switching to boinger's then?