Have a Cateye Vectra on a Dahon, but the same 70cm thing. I recall measuring the distance and it being just over or just under 70cm, but it does work. If the bike shop will refund you if it doesn't work, you can always put the transmitter and the computer in position (but not tie them down) and spin the front wheel to check. Or get a Topeak X'tender or something (had the Minoura Space Grip before, by the way, but prefer this - no plastic chrome and much more configurable).

Just done my first 100 miles on the new bike, so really happy...