It does not matter much, there is enough room for each nose to not be required to be in the center of the headset. Just shift headset to match both eyes and you'll be fine, your nose doesn't need to be fully centered
I have a 66-68mm IPD and tried the Reverb G1 with its 64mm. To me, that was usable for 60 minutes - then it increased eye-strain. World scale is off, you will be squinting, and be nauseated when you exit the headset. That is solely because of the mismatch of IPD being too large.
You need something in your IPD range, and at 71mm, that could only be the Index. You can max out the IPD slider and bring it up as close as possible to your eyes with the eye-relief function, which will further increase the possible IPD range. I would not mess with image stability and proper alignment.
I do not recommend the Pimax headsets anymore since I have received the 8KX. I've had the 8KX since September but just couldn't keep using it. It messes up your vision's stability, it's a real health hazard. They did change the lenses or lens distance to screen from the 5K+, if you read something else, that's simply a lie or wishful thinking of users. As a result, it seems the lenses do not break light to fit the view properly anymore as they'd be supposed to be. I went to the doctor to get measured, I had one eye rotating off to the side after using it for a few hours. He confirmed it by measuring my IPD multiple times and it would fluctuate. I also had the sensation of mismatched eye-rotation when waking up in the morning after playing 2-3 hours in the evening. Repeatedly. Basically, my left eye rotated left, my right eye to the right, and when opening the eyes it would take a while to re-focus. Pimax headsets, especially the latest generation, are hack-jobs. The original 5K+ had its lenses designed just for it - by people not working at Pimax - but Pimax didn't redesign them for the 8KX's different screen sizes, distances, etc. Probably because redesign + retooling is easily north of xxxk, given the size of these lenses. Plus the same high cost range to get an automatic distortion-profile programming per unit after assembly, which they still do not have. I know, I do not assume; they update global distortion profiles via patches, which make it better for some users and worse for others due to assembly tolerances. Now, each HTC, Oculus or Index (and thus also Reverb G2 due to the cooperation) come with individual distortion profiles per individual headset written into their Firmware. Not based on SKU, not based on batch or revision. Individually. So Pimax is a hack-job to me now. They also do not refund, so be aware.
I wanted to write the Reviews on G2 vs 8KX by now, but as you guys know, the G2 hasn't even been shipped to Europe yet at all. So it may just become an 8KX review.
Addendum, when re-reading this: I know some guys were lucky with theirs. It seems to have been a similar thing in the past - my 5K+ (sn204) was really really good. Other 5K+ owners reported terrible experiences. So there may be some 8KX that are circulating that may be good. The fact that the quality is not assured at all is enough for me to recommend to friends to not getting a Pimax headset.