A couple of things to add would be to shut off anti-ice, if possible, if in use, and cabin heating. Try also to "skyline" your previous track, to check for a dark trail, or if you have a strong shadow ie above cloud , it may give you confirmation..., or not. Turn off all non-essential electrics, as every little helps.
Another airmanship point would be to have your Crit.Points for both engines, and s/e ,worked out so the decision to continue or return should be clear...