the problem will the in the chain/swing arm pivot area. the longer shocks will put too much of a angle on the swing arm and chain may rub/hit swing arm a lot more than usual and will rip through the buffer in no time. i dont recommend going this much longer. a better option would be to shorten the shocks, either by shortening shaft and or shorter lower eye, both easily done. chances are they already have too much shaft stroke for the 250 B anyway.