Nev Lush in australia has campaigned one succesfully.I think a club member has used one in the past..sidecar dug I would of thought that there have been quite few, as in theory the lusty h2 engine would lend itself to this type of motorsport.
A friend of mine was at the Wasp factory in Salisbury the other week, they are making a brand new twinshock MX chassis for a customer in Australia. who will be running an H2.
My EML project has somewhat stalled at the moment, credit crunch and all that sadly. I have a chassis, and an H2 motor and a wife who spends money on silly things like furniture and decor which could go to much more worthy causes...