Pretty sure the 4PKS has an 8V cutoff. Without some sort of bec to drop the voltage down, I think you're limited to the LiFE or NIMH packs. I could be wrong though?I just purchased a Futaba 4pks Radio, and am wanting to get rid of the dinosaur NiMH battery. Looking for advice as to what others have gone too as an upgrade. Lipo preferred, as I don't have anything that charges LiFe.