I've no experience of the Wilma system but a few years back I grew a friggin GANJA TREE using a 20lt bubbler system, no joke, main stem was thick as my wrist, reaped loads, got some photos somewhere... it was as big as a small car lmao. Hope helps...
i would stay away from a wilma because of the space of the plants its fine for when there young of even if u trim them alot but triming is not recommended plants need space to let light to bottom buds and to let air flow inbetween plants but thats what i believe and i have been told