imo your goal should be to not have these suckers cut off but to have a plant which is fully productive everywhere depending on situation, i usually will snip off the bottom 2-3 branches up to possibly 7 depending how monster it is for my grow but you need to realize the time spent growing these suckers then cutting them off and waiting the extra week accumulates over time to less yield over time cuz ur snipping so much.
if u time things right for your setup you only need to cut a few branches off the bottom (sometimes) before flower, giving a channel of airflow above the top of the soil and below the canopy, rising upwards to your exhaust fan, remember that leaves are transparent, light goes through them, and that the fan leaves act as power plants... they are not shadowing anything with the proper light penetration. hps and Led are very different games look into canopy penetraiton
lst and training techniques rather than cut things off