This thread has a video in the first post which might be useful...
Assuming the 10-15mm (max) ideal shell fit is measured right there at the bottom part of the stick in the pic above, the difficulty is that the rearmost portion of the heel is about an inch or so above the sole bottom, and moves into the rearward curve of the boot shell behind the heel. Easy to see and get at (from the side and above) with the boot cut off as shown, but in a normal boot not so easy to see and get at.
I'm in the process of checking out some different boots. Here's a pair of 10 year old Head RS 80's (BSL 317mm), and a new pair of Lange SX 120's (BSL 316mm). Both size 27.5/27 shell...
The boot board (zeppa) in the RS 80 is 12mm thick at the front and 30mm thick at the rear! The SX 120's boot board is 3mm thick in the front and 10mm thick in the rear.
I poke around in thrift stores a lot and last summer the RS 80's caught my eye. They looked to be in pretty good condition, and were the same BSL and last width (103mm) as my current Head boots. I yanked the liner and the shell fit was pretty good, and they were selling for $19.95, so I snagged em. I mainly got them because I play around with some exercises in ski boots at home, and also could use them for adjusting bindings, and my regular boots are usually kept elsewhere. Wasn't planning to actually try and use them for skiing, but I did take them out for a few runs end of one day this season. The fit was very snug, (not a bad thing), and without shell mods I had some hotspots (bony protrusions), but the main thing I remember is that after just a run or two my quads were really complaining (problem I don't normally have). Looking at the ramp in that boot board I think I now understand why.
I seem to be right on the cusp of a 27 shell typically being just a little longer than I would like, and a 26 shell being a little too short. The 27.5 SX 120's with the stock liner and that boot board definitely feel loose all around, so I'm going to try an SX 120 in a 26.5 and see what kind of fit that provides.
To answer the original question - yes. ;-)