If you are using a skimmer, what dimensions? I would make the drain section big enough for your skimmer, heater, etc. plus a little wiggle room.
Will you be using an ATO? If so, the return section can be pretty small. If you are manually topping off and have a lot of evap, you might want it a little bigger. Otherwise, optimize the size of your 'fuge. More area there means a larger macro crop, which means more nutrient export.
I would put a ball valve on the line going from the T to the 'fuge, too - so you can control flow independantly to the DT and 'fuge.
Not to start a fight, but I would guess this method is at least as common, if not more so, than feeding a 'fuge from a drain line. Drains can be finnicky and hard to tune if they're split or otherwise complicated. And, since skimmers work best on "big" stuff and macroalgae does best with the well-dissolved nutrients skimmer miss anyways, IMHO it makes sense to skim/filter your water before you plumb it to the 'fuge, which supports T'ing off the return, not the drain.