I use the insole for my redwing boots, it works perfect, but I still want a boot that fits just right.
That's understandable and I completely agree.
But I found it work if push comes to shove
Have you asked Aero whether it would be possible (and not financially crippling end price-wise) to knock up a size 6? I'm not a shoe/bootmaker so have no idea if it's a easy business or a difficult pain in the backside. Might be worth asking them the question though.