Shawn knows his shit, I back shawn... Too may years of boot fitting myself... errr... retail...
get a good orthodic too, not some limp fish dr. shoals, even those surefoot ones suck, my personal favorites are 'Superfeet' full cork. they are totaly worth the 150 bucks, they last 5 or ten years too. Just make sure who ever makes your cork can explain to you what 'Subtailor Neutral' means, if they can't... go somewhere else.
PS subtailor Neutral is a term in reference to the subtailor joint in the foot. The subtailor Joint controls the pronation/supernation of the foot. In a ski boot you want NO pronation, and NO supernation, (ie neutral: SUBTAILOR NEUTRAL. 99% of all peoples feet pronate, its how your foot adapts to walking over uneven terrain, pronation in ski boot = bad, reason being, when the foot pronates it elongates, and gets wider creating extra pressure on the toes and the 5th metatarsal, that little hot spot you get right on the outside of your foot behind your little toe. It can cause problems other places in the boot too.) On second thought, if they dont know about pronation and supernation you probably shouldn't get your boots fit there either.
oh you might as well shell check the boot too, take the liner out, stick your foot in, slide it all the way up to the front of the boot, so your toe is touching the end of the shell. reach down behind your heel, and you should have at max 1 and 1/2 fingers width of space from your heel to the back of the shell. ANY MORE and its TO BIG A BOOT.