I tried parabolics, replaced them cursing all the while, saw the results from the scrogged plants I vegged with them and put one back in the veg tent.
I ran 2 of them side by side in 1 tent, all good at first but they got so leggy! I'd never had a plant finish above 36" before and these were 4'+ going into 12/12 wtf??? They were MM and NL, growing past the (regular) reflector. With a new tent I vegged JW and ended up doing an emergency scrog in the bloom tent.
While they were chugging along, I came across evans181 grow here using the same reflectors but he did ok. A wtf? moment again.
He has his reflectors higher, so the light can reflect off the walls. Ahhh... that must be the secret thinks I, they do seem to kick more light out to the walls than directly underneath. Mine were as low as poss, couldn't even have a fan blowing on them. More light to the walls, more to the plants etc. Doesn't sound right but then I harvested the scrog, bugger me, I'll settle for that harvest every time. Back went the umbrella in the veg tent, I'm such a whore.

Haven't put them back in the bloom tent but at some point I'll give them a fair go.