Quote Originally Posted by wisright
my question is, if i really have to top it or tie it down, which will cause the least amount of stress to the plant.
and is there another way to slow its growth?
Tying it down is better than topping at this stage. I think you will be fine with those 2 strains though. The lemon should be nearly finished stretching and I've never seen a blue-cheese stretch very much beyond 2 weeks.

One thing I've done before is hang something like a X-mas ornament on the top to weigh it down just a little, once the top starts getting heavy it will start sagging a little bit on its own.