For the record, here is a photo sequence illustrating a reliable way to reduce the height of a commercial grinder by cutting down the hopper. I've done two, same method. La San Marco SM90 and La Pavoni Zip, both local kijiji bargains.
The whole job takes 10-15 minutes or so with minimal risk of damage.
I had briefly contemplated other approaches, including using my bandsaw, but this would have required a fixture, or some risk of damage if jigged only in a minimal way. Cutting by hand would have been a slow and tedious process. The Fein tool I used (and other oscillating tools) cuts a very fine kerf and is not as aggressive as any power saw and is therefore more controllable, if a bit slower. (not materially so in this case)
--Clamping the Fein tool in the vise with its blade parallel to the benchtop means no measuring or marking.
--The tool must be clamped firmly so it does not move during the cutting process. Too firmly might crush it, so a little care is required.
--Using a good flat bench itself as a fixture is always a good plan, and in this case it really makes sense, not only for the cutting but for the sanding as well. See photos.
The LSM had been trimmed before, the newly-arrived la Pavoni ZIP/sprint (Obel Berega) does not fit beneath the cabinets.
This is the multitool clamped in a vise on a workbench. The blade is set above and parallel to the surface of the bench, at the height of the amount you want to remove from the hopper. The relationship between the blade and the top of the hopper is therefore fixed and controlled by using the bench as a registration surface. The tool is very controlled in how it cuts. All of which is perfect for this sort of job, and if the tool doesn't move it is impossible for the cut or the hopper to stray. More aggressive saws will be much less forgiving, will require more extensive jigging (or risk) and could have explosive results.
Cutting now. See that a small section has been left intact. This keeps the hopper solid and tames things till the end, when you cut out these little "support sections" once the rest is done.
Turning the hopper, continuing to cut, moving it along the blade surface as well to prevent too much local heat build up.
Cut complete, now sanding on the flat of the bench - the Fein left a nice flat surface and the bench ensures it is sanded factory-flat. I started with 80 grit. moved to 120 then 220. (IIRC) To soften the corners, I left the paper on the bench and tilted the hopper while rolling the edge on the paper. For the inside edge, I wrapped the paper loosely around a roll of paper towels, and clamped that in the vise. used that soft sandpaper cylinder to sand the inside cut edge of the hopper.
For both the Pavoni and the LSM, the lid fit perfectly after cutting.
Done. Plenty of grinder capacity now!
La vita e troppo breve per mangiare e bere male.