Unfortunately there is no recommendable way of how to adjust large binding for small boots.I?d check with the shop you bought them and try exchange for small. This also means re-mounting of the binding.
Best regards from Black Diamond
-Would it work to change the wires to smaller ones?
It wouldn?t change anything since the cables affect only flex level. The difference is made in front metal toe box which is for boots up to mondo size 25 smaller (narrower) than for 25+.
Black Diamond Equipment AG