When do I lollipop?

Personally I'd lollipop long before flowering. The longer you wait the more stressful it will be, as you'll be taking larger cuts off and more. Now if your growing photoperiods and you take clones, then waiting is better as you'll get clones out of the first few branches you lollipop and they'll be bigger. I try not to cause any stress in flowering except spreading the plant out a little ( slight LST ) or selective defoliation to expose bud sites. You don't want to cause stress in flowering because it will slow bud growth. Do all your training, defoliation, cloning in veg for the best harvest. Just my personal opinion