I bought the boots from a shop in Colorado that shipped them to me. I didn't want to send them back but I think I'm going to. After looking through all of my shoes, most are size 11 - only one pair is a 10.5 (must just run big). I also know that K2 boots historically run small so getting a 11.5 sounds normal. I also found out that they are full-size differences - not just different liners or insoles.
The stock insoles are JUNK. I actually sent pictures of them to K2. For a higher-end boot, I was shocked to see what came out of there. I plan to buy Superfeet or Sole insoles.
The boots are snug when standing. My big toe is slightly curled (scrunched) when standing straight up. When leaning back on my heel, it definitely gets tighter. I'll put them in the mail tomorrow and get the 11.5.
Here are pictures of the junky insole...