I have been running Spektrum for a couple of years now. I must have 7 or 8 receivers, some with 6 volt batteries and some with 4.8.

To date I have not had any problems with receiver lock outs. Only precaution I take is to make sure my batteries are fully charged before going flying!

With regard to the 6volt 2000mAH battery the only thing to be careful of is how you charge it, especially if you use the charger that came with the radio. These are intended to charge a 4.8volt battery at (I think) 50 or 60 milliamps. It seems that they will charge a 6v battery (never tried it myself though), but it will take a very long time.

Good luck

Terry