[mst]

I would still have gone with a higher length for the meta stuff, given the 2730 character limit on indexing I'd've thought 2048 would probably be fine and much less likely to result in a long path unexpectedly ventilating somebody's foot.

If space abuse is a vector under consideration, given there doesn't seem to be a restriction on the number of entries (if I somehow missed one my apologies) you could easily stuff it with a really big array of 255 character entries so I wonder if 2048 plus some sort of reasonably generous limit on the number of elements might not achieve the goal better and provide a better UX/DX as an added bonus.

(I'm currently working on a design in a somewhat related area so I've been doing a fair bit of thinking about this - I may of course still be completely wrong, but if so I can at least claim I put effort into ending up wrong ;)