Toyed with the idea of doing it on a singlespeed, done a lot of training on one, or should i say with one over my shoulder. Did last years with a 34x27 low gear, but noticed a lot of people with mtb mechs and cassettes on. My bike's 'peaked' now with a 34x32 low gear. My theory is, if i grunt and grind in training on the singlespeed, pedaling the other should be less grunty, grindy.
As with all things..........we shall see
It will still hurt though, but its a nice hurt