Well this is typical, turns out now, after having the 46/34/24 TA Chinook chainrings fitted (with an 11-32 cassette for now), that when on the 11T cog in the middle 34T chainring, the chain catches on the TA chainring pins (the original SLX ones must have been less protruding), so 11T/34T (83.5") is unusable, leaving 11T/46T (112.9") as the only usable gear with the 11T cog! Not going to see much wear on that then...
Has anyone else experienced a similar issue with TA chain rings? I guess I could try to file the offending chainring pins down with something, but not sure it's worth it. Slightly annoying, as the nearest gears either side of 83.5" are 76.5" (12T/34T) or 77.6" (16T/46T) and 88.7" (14T/46T), so it does sit a bit in-between these, though perhaps close enough to 88.7" not to be an issue. I guess in most case I would probably have changed-up to the 46T chain ring before then anyway. Not sure if I will have the same issue with a 12T outer cog, but I wouldn't be surprised!
BTW the 11-32 XT Cassette cog sizes are 11 / 12 / 14 / 16 / 18 / 21 / 24 / 28 / 32