I just leave the 1/2" drain wide open, and I get a trickle on the 1" emergency (and sets the level closer to the top). The shorter the 1/2" drain, the more flow will go through it.
I did the same on the return, but just used plain elbow instead of loc line. I use a dc return pump and noticed if I use the loc line, I have to run the dc pump at level 5 or 6 to get the flow right. But with elbows, I can get the same flow at level 2. This tells me how much flow is restricted/lost in loc lines. Probably won't matter to most people, but I am trying to configure the least energy consumption for the tank. The 1" drain is able to take it even if I crank the return to level 10. and if both drains are clogged, the return section water will not overflow the dt, and the dc pump will automatically shutdown after a short period of time running dry (I think 30 seconds), so this takes care of ATO from running amok. the dc pump does not restart even if dt water flows back down via return line after it is shut down due to running dry, and has to be unplugged/re plugged to start. you cannot do this with ac return pump.