My boots were half a size big and I brought them to a ski shop that did boot fitting. They cutout a cardboard-like material about the size of your insole to go under the liner in the boot, lifting it up a bit.
This did wonders and cost me $20 I think. Would be pretty easy to do yourself.
The other guys were saying that getting insoles to raise the heel would give me less foot length and allow me to fit better into the 13s. I guess in your case it made your feet slide forward so your toes were at the end., but I bet that that's because you had a lot less friction. Interesting.