Back to the OP query, I spoze the piezo Bongo more
"deserving" of the Cobalt flats would be the one with
more magnetic PUs, since Cobalt is about magnetism
and has no added benefit for the piezo saddle PUs.
Consider radically lowering the mag PUs when you
switch to Cobalt. It allows you to do that and still get
a healthy signal. There's a cool sonic effect to having
more distance in there, but most strings and PUs will
lose too much output. With Cobalts on a Bongo you
can do it with very little output loss [as compared to
same bass with conventional strings] cuz you got the
neodymium PUs, the Cobalt strings, and the Bongo's
powerful, and quite clean, 18 volt EQ-pre.
Admittedly, I'm piezo oriented. Many of my basses
have no mag PUs at all. So realize you're reading a
suggestion from someone who treats the piezos as a
primary voice and the mag PUs as added coloration ...
prolly the reverse of the more typical approach. But
the flats do enable this approach. If you play fretted
bass and favor the piezos, you can get far more fret
noise than you'd want when playing RW. Flats, any
type, will reduce fret noise [vs RW]. Acoarst most of
my basses are 200% fully immune to fret noise
