On the Gen 3 (and i'll bet it's the same on the rest of the 3s motors too, as the blocks didn't change much) the head oil drains are on the intake side.
I don't understand how adding a 4th drain to the intake side would have helped as the oil is more likely to pool in the exhaust side of the head.
In fact, you can see from the outside the large drains cast into the block on the intake side. They are monsters, at least half an inch, probably closer to 15mm ID.
The beams motors have an external drain on the exhaust side, ie. the opposite side to your extra drain.
From what i can see, the oil pooling issues can be easily solved by the following (ref gen3)
1. Mounting engine with a slight (even very little) lean toward the intake side.
2. Bigger sump to allow for the oil stored in the head
3. Restricting flow to the head by tapping and inserting a restricter into the head oil journal.
I'm not sure that the gen3 gasket restricts the flow as a well respected toyota performance engine builder in Melbourne recommends fitting of the restricter in the head on gen 3 motors for high RPM use. This may be in addition to the gasket restriction though.
I too speak from experience. I'll post some pics of my build tonight.
It is possible to port and plumb the exhaust side for oil drains. I'll do this if I encounter any problems