I suspect that the 90 gr load shot better due to the size of the slick. If you cast up some of those 434470's from 16-1 wrapped in that 8 lb paper , with a single thick Napa rubber cork wad, on top of 74-77 grains of that 2f you may find just as good if not better accuracy.
I messed around for quite a while with the smaller diameter bullets, but didn't find consistent good accuracy until the diameter before patching got to .434 -.435.
