Battery Choices

[isuck@rc]

Well i have several choices of zippies for my Revo's that i'm assembling (at the horrible stage of installing the motors and escs) one is running a pletty/shuzles 18.97 combo (only good for 5s) and one a tekin 2250 rx8 combo.
I'm currently eyeing up some new batteries for the pletty to run a straight out 5s set up and just curious on riunning paraell or series so ie two 5s small batteries like the litestorm vx series in their smallest combo (think even these are too big for the e revo chassis) or miss matched batts.
Ie if i run a 2s and 3s that have sam Mah and C rating they will be compatible in series correct? For 5s?
Sorry for the stupid questions but i think after spending nearly $5000 Australian on my two trucks i better not skimp on the batteries and the current supply of batteries is not suitible can be become test pigs for my stampede vxl and the slash im going to race in stock trim.