the more vertical the shock, the more effective it will be a dampening. But if you angle it you can get more travel out of a smaller shock.
So if you angle it forward a bit, you should be able to get around 15-16'' with those 14'' shocks.
if you had 16s..should be able to get around 17-18 at the right angle.
But you'll have to valve them a bit stiffer for them to be as effective at dampening.