There are a few things that can affect people's eye strain. Most important is the IPD in a fov outside what people are use to is harder to dial in. Thankfully the latest Pitool has an IPD offset slider.
I am pretty VR hardened after being in the Rift so long but I did get a bit of eye strain because of the Pimax not lining up perfectly at or near my IPD _(66.7 official).
Even after adding a Vive Das and a 5 ounce counter weight to it, (headset wants to ride forward) I found no ipd afforded perfect focus in both eyes at the same setting. The offset slider fixed this by allowing me to dial in a slight adjustment. The final piece of the puzzle was the headset still wanted to slip unless I tightened the DAS to a point where I felt too close and it felt uncomfortably tight.
Today I received my StudioFormCreative comfort strap
https://forum.pimaxvr.com/t/new-comfort-mods-for-pimax-head-strap-available-to-buy-now/13972
Put a big smile on my face. Now the Pimax sits exactly where I put it and I can wear it more loosely with glasses without pinching for hours.
This being a unique product, it has some teething issues for sure and it for sure is not a one size fits all solution or a one solution solves every ones issues but finding the right fixes has made this an exceptionally good VR experience. As a Kiickstarter backer I am quite pleased. Retail customers might want to wait for Pimax to advance the software more and release their DAS's unless they are hardcore VR enthusiasts and willing early adopters.