gear stat caps

The other day, I got the ability to meld materia onto gear with my lvl 21 weaver. Wanting to try it out, I tried to meld some materia onto my leggings (HQ Cotton Chausses).

Now the in-game help that explained materia melding made absolutely no mention of there being such a thing as stat caps (which I think it really should have talked about). But because I frequent the forum I at least had an idea that some sort of caps exist. What I've seen mentioned, though, is that the caps often make it impossible to (usefully) meld the same stat that the gear already comes with.

OK, well, Cotton Chausses come with just a Control boost, so I figured I could safely add Craftsmanship. But when I tried to add a tier 1 Craftsman's Competence Materia (craftsmanship +3), it gave me a warning message that the gear is too low-level to make full use of the materia. Why? It's the lowest tier of materia there is, and was adding a stat that wasn't already boosted by the gear's normal stat boosts.

A bit of trial and error, and I found that I could add both a tier 1 Craftsman's Command Materia and a tier 1 Craftsman's Cunning Materia, so I got a +1 boost to both Control and CP, but I still don't understand why it allowed me to add an extra point of Control to a piece that already had Control +13, but wouldn't let me add a +3 Craftsmanship when that hadn't been boosted at all by the initial stats.

Shouldn't there be some sort of logic to this system, or else a way to identify what the caps on a piece of gear are? I couldn't find it.

There are posts with the numbers for the lv 50 crafting gear sets (and the patrician set, too). There is no logic behind some of it, and the lists have been made by folks who did what you did. Will it take a +6? How about +5, +4 and so on. For low level crafting stuff, I doubt there is a list made. I guess that's the bad news, melding lower stuff, you'll have to find out each piece individually like that. If you can make/save a materia of each type and level, it should be an easy enough process until you get to the 50 stuff which is already fleshed out.

Irritating and silly, but that will be the necessary evil.