downside to recirculating drip

sounds like a Wilma etc... you will not acheive massive effects with these systems without adding RDWC/aero to them to get big yields

they are good to be left alone for a few days.. i cant do that with my AF60 i would be in big trouble!

if it is a wilme etc then be careful about the delivery manifolds as they are different depending on how many pots you have and the old 4 pot one was a really poor design! the 8/16 etc were ok though

So from what I can see your growing in your roofspace... I'm not sure exactly what you mean by recirculating drip however I'm a coco grower and to me, this simply means re-using any runoff from your drip feeds... the downside to this can be pithium/root rot, flucuating PH, and potentially an 'incomplete' feed depending on what the plant wants to take out. For this reason, a decade ago I moved to drain to waste... minimal runoff means not much $$ lost... IMO drain to waste with coco is teh way to go... also this is very safe in a roofspace! Stuff having a few hundred litres in your roof area! When somehting goes wrong that's alot of water coming down - I once knew a guy who had about 12 E&F tables and something went wrong, a couple of hundred litres went down through 3 levels of other peoples apartments!

depends on your medium, for growrocks, I would use flood and drain instead, it will require less work to setup, the rocks will be watered evenly, and the drain sucks in fresh O2 for the roots. also there will be no algae problems because I flood below the level of the rocks not allowing the surface to get any ferts