i tie mine down mate so the tallest one i have is 77cm from pot to top and it is already 4 week flowering so it aint growin no more. you should definately tie em down if your limited on space, have you started a thread? give it a good name, put pics up and everyone will want to get there 2 cents in.
p.s have you already got a room setup?
p.s have you already got a room setup?