IMO definitely no QT in a sump/fuge. that kills all the purpose of a QT. you cant dose copper in your sump, but you sure as he;l will have to if any of your fish will get ich.
better use the QT space for a bigger fuge. fuge should be anywhere from 1/3 to 1/2 of the MT volume for a successfull nutrient removal. this is based on what Squidd told me some time ago.
baffles by the return pump should be 3 in order to eliminate any micro bubbles, and the second baffle should be higher then on a pic. the proportions will look different onvce you calculate the backwash area and determine the ratio of overflow area : fuge : return pump. also make sure that your fuge will not be getting too much flow. oh forgot to ask, where will your skimmer be. is it in-sump or external skimmer. if external then you need to incorporate it in your design. if in-sump, then use the space for QT for the skimmer, though i suggest that water from the fuge should not be skimmed, but should be pumped back to the MT, and the water from the MT should go into the skimmer and then into the fuge for extra malnutrient removal.
ill attach a design that i was originaly planning to use, but desided to have the fuge separate from the sump, which gave me volume ratio. if you want good info read hreads 101 and 102 on design, calculations, and plumbing.
good luck
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