Yes, It's a close shave.
With the ZM25 +1 m front filter you need to remove around 0.6mm. so grinding a bit the adapter isn't enough, but it may help if your lens has fewer shims inside than Samuli's, for instance.
In the case of the ZM35 + PCX 5000, shaving 0.2mm might be enough in order to avoid removing shims when the user feels uncomfortable messing inside the lens (although it's very simple task if you have a spanner wrench)
Anyway, I advice to try the shim solution first. Only if the lens has no shims inside or it's very complicated to disassemble you should try grinding the adapter. It's a very tedious task. You need lots of patience and a good caliper. Not easy at all to achieve to achieve an even thickness around the ring. Only 0.02 mm. off and your corners will never look like Choppy's.
