[TheSalche]

Raising 6th may hold some value here, his call suggests:
(a) he doesn't have the boat, but the pot's big enough for him to give it another shot on 7th
(b) he has a boat, but he's afraid you have 9's full, so he plans on check/calling 7th
(c) he has a boat, but he's hoping he can go for a check-raise on the river

from the way the hand has played out, i don't think he has the boat (yet), and raising 6th gives you the extra bet, and i think when you caught his king on 7th it becomes more likely he didn't fill up, and he is very likely to call with trip dueces, so raising 6th isn't terrible