ideally you should top them while they are small, let them grow and build a thicker stalk and main cola stem before flowering. that will increase you bud production greatly. By topping when you did, you should be able to at least grow what you would have before topping even if your plant is a bit squattier. I usually top them, wait a bit, top the two main colas again producing 4, letting it grow building stalk and stem size/strength then flowering. you can see an example of one of my plants just under 4 weeks 12/12 here:
http://boards.cannabis.com/basic-gro...y-anybody.html
I just posted the pics today.
Hope this helps.
Elway