When I ankle carry, I carry my 642 in a Renegade Cozy Partner 500. Best ankle rig made IMO. Anyway, I hate it when people say "I THINK X would be too heavy or whatever to ankle carry." If you've never tried it, it doesn't make much of a judgement. I'm tempted to get a Renegade for my 26 and give it a go. Yes heavier but also double capacity.
With that said, I would still probably run the 642.