This literally copy-pasted from an earlier post I created back in early February, however, rather than bump a thread titled "Direwolf Set Materia Cap Request", I figured it would be better if I created a new thread. Plus, this way, I own the OP so people don't have to dig to find the info, etc. Without further ado...
A majority of the following information is an estimation and is untested.
I'm using the same method that I used to hypothesize the i70 caps as seen here.
Note: In efforts to condense the list as much as possible (thus revealing the pattern shared across all pieces of gear), the following caps INCLUDE the amount of whatever attribute that is already on the piece of gear. In order to find out how much additional attribute you can add with materia, please subtract the amount of whatever attribute is already on the gear from the listed cap.
Note2: The following data doesn't apply to non-standard melds unless otherwise specified. Melding something like DEX onto tank gear, PIE onto non-mage gear, etc. would fall into this category.
Attribute caps for iLv90 Weapons:
• [Main Stat]: 31(2-Handed), 22(1-Handed)
• SkillSp/SpellSp/Crit/Acc/Parry: 37(2-Handed), 26(1-Handed)
• Determination: 26(2-Handed), 18*(1-Handed)
• PIE: 28(2-Handed Healer), ??(Everything Else)
• VIT: 35(2-Handed DoW), 25(1-Handed DoW), 32(2-Handed DoM), ??**(1-Handed DoM)
• Elemental/Status Resists: No Data
*1-Handed Determination value is more of a guess than usual, as there are no i90 1-Handed Determination values to go off of. It probably caps at 18, but I might be off by 1 or so.
**No 1-handed DoM i90 weapons exist currently, so these values are unknown
Attribute caps for i90 Shields:
• [Main Stat]: 9
• SkillSp/SpellSp/Crit/Acc/Parry: 11
• Determination: 8
• PIE: 8(Healer), ?(Everything Else)
• VIT: 10(DoW), 9(DoM)
• Elemental/Status Resists: No Data
Attribute caps for iLv90 Head, Hands, Feet:
• [Main Stat]: 18
• SkillSp/SpellSp/Crit/Acc/Parry: 21
• Determination: 15
• PIE: 16(Healer), ??(Everything Else)
• VIT: 20(DoW), 18(DoM)
• Status Resists: 4
• Elemental Resists: No Data
*I'm told that the DEX cap on tank gear in these slots is 13. While I do trust it, I haven't seen picture evidence.
Attribute caps for iLv90 Body, Legs:
• [Main Stat]: 29
• SkillSp/SpellSp/Crit/Acc/Parry: 34
• Determination: 24
• PIE: 26(Healer), ??(Everything Else)
• VIT: 33(DoW), 29(DoM)
• Status Resists: Probably 4, but I still need confirmation
• Elemental Resists: No Data
Attribute caps for iLv90 Waist/Ears/Neck/Wrists/Ring:
• [Main Stat]: 13
• SkillSp/SpellSp/Crit/Acc/Parry: 16
• Determination: 11
• PIE: 12(Healer), ?(Everything Else)
• VIT: 15(DoW gear), 14(DoM gear)
• Elemental/Status Resists: No Data
*Please note that as of this post, only the waist slot is meldable.
Updates:
2/26/2014 - Added some status resist caps.
4/2/2014 - Added a possible DEX cap on tank gear for the head/hands/feet category
If you have information that fills in some blanks or contradicts my hypotheses, please let me know.