No neither of those batterys would I ever use. At least not a full house airplane (meaning at least four servos or more) or posibly just a small parkie.

I would never use a four cell pack for any 2.4 system only five cell this especailly so with Spectrum that had all those early brownouts when the fellows used four cell packs. The capacity you choose is fine but I would also suggest five cell Nimh. Five cell Nimh is what I use in the majority of my fleet.

Regarding polarity that does not make any sense are those batterys not center pin l positive? The only reverse polarity that I am aware of currently is the long standing and irrational penchant for JR to use a centerpin negative two conductor charge jack on their transmitter not the Rx pack.

John