Topping/FIMing

I have read the grow faq's on topping and FIMing, but I need a little clarification. At what point should I start doing either of these? Consider that I have a 2.5'x2.5'x5' space to work with (How do I fix the heat in this room? (Diagram included)) and even less height with the light in there and heat as well, so I need to maximize production by making my baby a little bushy I'm thinking.

let's try this...here are three pictures. does it look like she is ready to be topped or FIMed? and if so, which would you suggest? also, if you see any other problems, let me know...this is my first grow. keep in mind, like a dumbass i burned the bottom set of leaves pretty bad the first day under the new light so thats why they look a little funny.