Fimming helps to get more branches then a simple topping.
If you've got a little extra time to veg, you can utilize all kinds of topping techniques. Just don't use any topping techniques (unless you must) while in flower, or maybe even a week or two before switching to flower.
Personally, I'm a big fan of Uncle Ben's 4-cola topping technique. It's easier then fimming, and gives me more consistent results (in my perpetual setup).
Hey, what node did you make the cut at (cotyledons don't count as a node)? I'm just wondering because Uncle Ben's technique tells you to do it at first node for 2 colas, second node for 4 colas, but I cut mine at the 4th node, and I'm not sure what the result will be. Also, how is your plant doing now?
Looking good, I think mr bill could use some N though. Just a thought to throw out to you, remember with the extra growth on the plants they are going to need a bit more goodies than single cola plants on average. Good Job