[Tyson]

Perhaps i didnt explain right, tried to make it as simple as possible this time!

Connecting the BEC input wire from the SPX8 directly inbetween 2 saddle stick packs (4s) is apperently the best method as LRP only make stick packs no more than 2s. (They designed it around there product line not a 3rd party battery supplier)

The MANUAL states that if a single 3s or 4s battery is used, then you must correctly identify the the right pin on the balance plug of the 3 or 4s battery.
(This means that you are taking the supply voltage and current drain from particular CELLS within a 3 or 4s pack which also combined with other CELLS in the PACK supply the ESC)

*Perhaps this current drain from powering the RX, PT and servo on particular CELLS within a 3 or 4s PACK, could posibly leave those CELLS within the PACK at different voltages? i.e UNBALANCED CELLS in a PACK*

*Perhaps it might be better, if you use an external BEC when connecting a single 3 or 4s battery pack with the LRP SPX system?*

*IMO

I am also not telling anyone to go buy this system because it is better than MMM, Tekin, Losi etc, i was explaining the operation as dictated by the manual supplied with the SPX8. (I just own one)