You need to verify that the length is "close enough" between the two boots. Your 26.5 is the inside size (the size that fits your foot). There should also be a marking on the boot sole that indicates the length, like 320mm or 318mm or 315 mm.
If your two boots lengths are within 5mm of each other, you should be good to go.
As indicated in other posts, the DIN standard will ensure that the toe height, width, heel cup, and other standardized measurements are the same.
As indicated in another post, you can also verify by stepping in and seeing if the forward pressure indicator on your binding is within the proper range markings.
Both of these ski boots fit my bindings without adjustments when swapping: (318mm 27.5 and 320mm 27)
Edited by pchewn - 1/6/17 at 4:49pm