yeah man-always start to LST them in vegge state of grow.but weed is really stong and tough plant and i think you can still tie it down 4 the topp, just be shure you do not brake it.also, if you want to keep them shorter, then in vegge or pre flowering state-topp them or pinch them-then you get more bushier plant, and in some strains, like blueberry-it can increase the overall yields.
keep it up man....