[Closed] Brakes question: what would you do?

Long-planned trip to CYB next weekend.
One of our group has Avid Elixir 3 - last time out (5 weeks ago) he couldn't get a new set of pads into rear as one of pistons wouldn't retract enough to get them in - admittedly they were after market pads and probably slightly thicker than Avid originals.

We're up against it time-wise now: so, take a chance on these or just buy new F&R SLX brakeset or similar? He's happy to change them anyway - just need working brakes by no later than next Fri and he's not really mechanically minded and short of time. Surely just get new? Any other recommendations? (Not talking £150 per end Hope etc).