What do you mean you won't jibe the pole? At some point you need to turn, thus you need to jibe. Dip poling is near impossible if you have a pole longer than J. Also consider how much extra weight you'll need to deal with at 1.3x J.
Additionally, just yesterday I was heading downwind wing on wing flying my 110%. Wind was at 12kts and rather flukey (common in SF Bay). The
jib was not fully cooperating, so I considered (for a moment) using the
spinnaker pole. I didn't feel like
rigging the foreguy, so I opted out. However, the length of my pole (equal to J) would have worked just fine. I speculate even better had I been flying the 140%.