It is always a little amazing how impervious conventional wisdom is to even reasonably analytical work like Sherman's. I can't speak with much direct knowledge about the UK, but 2.5's are virtually unobtainable in Germany and Austria. Based on my experiences, I would suspect a third to a quarter of the guns on any given drive hunt are 67mm sxs's or drillings. They are all now, and have been for a generation, happily digesting 2 3/4 field loads. Don't even know a war story about one giving way.
Sure, it is "better" to use 2.5's in a 2.5 chamber, but the real thing to pay attention to is pressure and, hence, load.
