IMO, this shouldn't even be an issue for offroad. Offroaders aren't going to buy 17.5's because they are too slow and 13.5's have already become the standard for BL stock offroad. Regardless, the 27T/17.5 class is just a recommended transitional stock class for club level racing whereas Super Stock/13.5 will become the regional/national stock class. Offroaders who race stock will keep using 13.5's at the club level until they are the official Super Stock motor in 2009. Some of us might have to sack up and strap in a 10.5 (or 19T) to be competitive at regional/national races in the meantime, but I think that's a small concession, which helps integrate the new technology into racing.