Hotswapping with very short (for sure under 0,25 second, via mechanical switch) paralleling of main battery with other small li-po - both behind amperage limiters - works great. Practically, it is 100% safe, due to very short time of paralleling + limiters = no way of extensive energy transfer between batteries (it's like one battery is charging another for <0.25 second...), but theoretically, it can be dangerous, so I don't advocate this approach.

In practice, I'm using mechanical hostwapping mechanism (inside Mugen Cover, no external parts) for > month on almost every battery discharge, and I don't experience any battery issues (voltage, internal resistance, capacity - all in norm). At the same time, i'm experimenting with capacitor design, that eliminate paralleling all-together. the problem is - most of the time - with size of capacitors Especially, that we wan't hotswap no matter of load. Seems quite impossible to pack up enough capacitors inside Mugen Cover, at least for reasonable price. Probably will change in future, ho ever, after tests I'm quite sure mechanical way is safe. Still testing and observing, though.

/Estel