From what I remember my 50 I-shock is 10.5" from eye to eye.
70 shocks start at 10.8" up to 11.5"
In the CRF70 forum there is a thread that I can't find right now, something about 70 swingers that had a kid who uses a 50 shock on his 70. He never really explained it very well, but I was thinking about it 'cause i'd like to go to a 70 frame/setup too. I was wondering if anyone that RIDES HARD has done this (50 shock on a 70). I can't stomach throwing another $350 at something that's only a quarter inch longer...