6.8 and thermal recoil

When running a REAP-IR thermal on a 5.56 AR, the recoil is minimal enough that you can look through the shuttered eye cup when shooting. Alternatively when I put the REAP on my .308 AR, recoil is significant enough to warrant removing the shuttered eye cup and just looking through the screen (at least for me, maybe I'm soft).

I prefer using the shuttered eye cup. I have not shot a 6.8. For those with experience, are you able to retain shuttered eye cup when shooting 6.8 AR or do you...

6.8 and thermal recoil