Actually, my overflow can handle my return pump, just not with the skimmer attached. Before the skimmer, I had the unadjustable Dolphin pump on, and a bioball on top of my 3/4" overflow, and there was no need to make any ball valve adjustments (both were open). Water fell down as fast as the pump could keep it up.
I understand having to slow down the flow coming down the overflow to the skimmer, and I agree. I wouldn't mess with that ball valve...especially with only having one overflow at the moment.
So, I just closed the ball valve on the return pump a bit. I slowed that down, which in turn slowed down the rate of water falling down the overflow.