Sizing down in ski boots

I went from 27.5 to 26.5 when I got bootfit. It’s kinda tight on the toes when sitting on the lift or whatever but as soon as I put a little pressure on the shins it’s perfect

You have two options:

1.See a bootfitter

2. Just buy full tilts

Ski boots should be snug, but never uncomfortable or painful. Ski boots which are too small for your feet can cause all the problems associated with shoes which are too small for your feet and then some. With heat moldable liners, you shouldn't need to spend a lot of days breaking in a new pair of boots.

https://orthoinfo.aaos.org/en/diseases--conditions/tight-shoes-and-foot-problems/

I measure at 26 but with custom footbeds I ride a 24.5. I can ski, coach or tour 6-8hr days with no issues. Probably 16 hr or so break in period for the liner. I think a good boot fitter is essential but it comes down to how you want your boots to fit and function.

Always easiest to start with the shell fit. Almost every brand/boot uses one shell to cover a whole size and a have size (with a thicker boot board to take up volume in the smaller of the two sizes.) Different brands break their shell sizes differently, though. Some break on the whole size (i.e. one shell covers 26/26.5, another 27/27.5, etc.), and others break on the half size (e.g. 26.5/27, 27.5/28, etc.) So a mondo size in one brand, or even one model within the same brand, is not necessarily equal to another.

Pull out the liner, and put your foot into the shell so that your toe(s) barely touches the front of the boot. Then look at how much space there is between the back of your heel and the shell. About 1 finger of space will be a tight fit, 1.5 fingers a medium fit, and 2 fingers a looser fit. Less than 1 means the shell is probably too small (or you're a racer), and more than 2 means it's too big.

There are lots of other nuances to look at when it comes to fit, but starting with the proper shell is 90% of the battle.

Just to add, if you downsize (1cm shell fit) then this size of boot should not feel great out of the box. 99% of the time it will require some stretching and/or grinding in order to be comfortable and warm. This is the type of fit that will yield the highest level of performance but it will take a few trips to a competent boot fitter to get right.