Mike,
After speaking to my battery supplier today (No BS), we were talking about two 4.8V 1650 Nimh packs that I have on the shelf running in parallel with two switches. We felt that this setup was more than adequate capacity and weight wise for the 1.20 sized airframe. Again, sport flying and IMAC basic, no 3D. The longest run will be 18" and I have all Hitec HD twisted wire extensions and Y'S, (I had some 18'S made from 24'S, as you don't offer them and wound up with two extra 6'S). Please have your factory think about offering 18'S as they are quite common in today's ARF'S.
I prefer not to go to 6V as I have had some big time issues with jittering with my other Hitec servos and IMHO a regulator is just something else to fail. The good news is that Tom Fawcett advised me today that a reverser is not needed for this airframe. The dual elevator system is set up for standard throws one up and one down.
Thanks for your time and expertise, Brian....