Isnt 6,6V a little bit to much? Fully charged an A123 pack will be 7,5v. I use Futaba 9155 digitals all around. They are specified for 6V but at 7,5V I start to feel uncomfortable.

I agree the KISS principle is good. Considering this having a 5cell NiMh might be an option, but I also like the consistency regulators give. I have not decided ultimately.
However to get back to the original question. If I would like to use a regulator, what options do I have? Two spektrum regulators are 100g of weight and $150. For this price I could as well by a power box and a cheaper AR9000 receiver. So before I decide what the best option is I would like to know what regulators people are using with the AR9100 receiver (if there are any).