Earlier this year I attempted to cross a BGS 9 1st Ed Base Mewtwo to PSA. The card had strong sub grades (9.5 centering, 9.5 surface, 9 edges, 9 corners).
I own a shadowless copy of this card in both a PSA 8 and a PSA 9 and felt the BGS 9 was waaayyy stronger than the PSA 8 and much stronger than the PSA 9. I also compared it to every high resolution scan of PSA 10 copies I could find and felt it had a (chance) of getting upgraded to a 10.
Between the strong subs, and my comparison to the copies I had on hand, I submitted it for cross grading with a 9 minimum requirement.
It did not cross.
Looking back I probably should have submitted it with an 8.5 minimum requirement to give them a little wiggle room if they saw something new once the slab was cracked.
I am skeptical of the cross grading service in general. They really have no incentive to run the risk of cracking the slab when submitter is paying the same amount whether it crosses or not.
Also, IF the card were to cross or upgrade, it would essentially be an admission that a competitor’s grade is equal to or better than PSAs grade so it’s really a lose lose for them.