NO DON'T TOP THEM!

I would train them using Low Stress Training (LST) I use cut and bent coat hangers so the look like long fish hooks and push them in the soil then gently bend the top under the hook so it is at horizontle position. This has the same effect as topping but alot less stressful to the plant.

You can also use heavy cotton string or butchers string and tie them down as well.

I have basically the same set-up as you, I have a grow log titled "day one" you can read that and see what I am doing and take what you might think will help from that.

LOL