Your problem is that you have one pair of normal boots and one pair of reduced footprint boots. The fact that you couldn't get your Salomons to even center in the medium bindings baffles me to no end. My only though is that you didn't know how to use the adjustments and the mounting disk to center the boot correctly. Not trying to offend but it is all I can come up with.
I would love to see pics of your K2 boots in the large bindings to see what they look like.
2011 Smokin Buck Ferton 155
2013 Flow NX2-SE
2013 Flow Hylite boa
Burton Stagger pants/jacket