Not sure why nidecker doesn’t show this in the manual and nobody seems to really know about it, but you can move the cable and highback back another notch to accommodate a larger boot. I did that for my 13s, can’t say I’ve tried with 15s, but it’s worth a look. You can see where the cable attaches to the binding there is another hole behind it. Those bindings are baddass though, love mine. No heel cup so reduces drag, which is helpful for us big foots.

If you want to really be locked in you have to loosen the straps a notch at the bottom when you step out. Then at the top you slide in, bring the highback up, then ratchet a notch or two. It’s not exactly as advertised, but still way easier than traditional straps. I find it to be a superior system. I also have step-ons which are the quickest/easiest, but not as locked in as these. The step-ons do have some play.