Never fished the spillway in the spring for walleye. Dead mid summer when it's the hottest I will hang out there for some huge catfish about 100 yards off shore in the channel.
As far as sonars, they, like june bug spinners, rooster tails, cpswings, worm harnesses, have had their day in the sun too at Pymatuning. Probably a five year stretch in the eighties it was the go to lure and EVERY bait shop on the lake had 100s in stock!
I used the heck out them on the north end with some success and an occasional snagged fish. The best however was a late summer day on the north end and we were just dropping them in a slow flutter and reeling up really slow. We must have caught fifty big white bass within an hour. What a circus.