Dunno, I wouldn't prune or trim shade leaves, but topping the plant at the right time causes it to produce 2 colas at the top, not something I'd do if you got a lot of headspace in your grow room, but if you stealth growing in a small cupboard, or doing a scrog, topping is worth it, as I understand it (I'm a pretty novice grower myself, but I recon I've probably read a whole oxford english dictionarys worth of grow tips, it's often hard to tell the good advice from the bad, since a lot of authors seem to just recycle the work of earlier authors without actually testing themselves). Hopefully as time passes, more growers will post here, as the only real way to learn directly from folks who've tried it, experience beats 'book learnin' any day.

Oh, sorry, and I don't mean to contradict you, bonbon, just adding my take on it (I'm in a bit of a bolshy mood, so I've probably forgotten my socail graces)