Electric Strings on an Acoustic?
My Sunrise works with Phospher-bronze..
I've just got one Fishman, and it works better with electric strings. I can't imagine how a simple passive electromagnetic pickup could be designed to compensate for the reduced magnetic mass of nonmagnetically wound strings, but fortunately our hearing is nonlinear enough that the apparent difference isn't as big as you might think.
easily: tailor the magnetic flux density in the vicinity of each string = change pole size and/or distance to string. works on regular "electric guitar" pups => note staggered pole pieces on Strats, adj pole pieces on many humbuckers. this can be done even on pups where the pole pieces are hidden or appear to be the same, in the latter, the gaps between pole pieces and main magnet can be varied. none of this is difficult.
"works better with electric string" could simply reflect your preference for your playing style -- valid, but doesn't mean the design wasn't tailored.
-=tension & release=-
"A cheerful heart is good medicine."