problem resolved - I'm going to Isle Royale in October. Sierra was a little too risky, given I just recovered from a compound fracture of my arm and a skiing-related knee injury. Failure was a very likely outcome heading out to the Muir Trail this late in the season, so I'm saving the gas and go local instead, visiting some moose and wolves at the very end of the season in that park - I'll be on the last boat back to the mainland...

This change of plans saves me enough vacation time to be serious about another April push on the Mountaineer's Route next year, when the -20F bag will be just right...