I'm no pro, but here's what i'd have to say to you based on my experiences:

18 plants in a 3.5 x 3.5 space is going to be WAY too over crowded unless it's a SOG. You say you are using latewood's recipe which i believe is meant for growing only a few plants, but growing them large and full. I know a guy who uses latewood's recipe (better than i do...) and his last harvest, he got 1/4 pound off each plant. He was only growing 4 plants, but he had plenty of space (roughly 8x8). I am currently growing 10 plants in a 3 x 5 area and it is incredibly frustrating trying to maneuver through the jungle. My top colas are nice, but there is very little light penetration down below.

Everything else sounds great to me. I would just suggest thinking about 2 or 3 flowering plants and giving them plenty of room.

just my twin Lincolns.

Skeet.