Thats nice work.
The Super Duper has been a favorite lure of mine – for bass! It has caught a number of them, almost without trying. One WAS without trying.
I had a biods nest on an overfilled spinning reel, and while I was messing around with that, the lure struck! It was a cold day as I recal, and thebass had that purplish tint they get in cold river water.
The Super Duper was a standard back in my dads day for trout, though. Ive got some originals from then… South Bends.
I dont know why your largest lure wont work – you appear to have most everything right. Have you tried spreading the legs somewhat, or taking out some of the curvature? It may also be as you supect: the long arm is a little to0 long. After looking at a lot of S-D’s, that is the one thing that jumps out at me
I hope to hear from you and to learn that you figured it out!