Shortman, being "leading", "advanced", and "lighter" can lightly lead this plane into an advanced position in the ground if you're not careful. I believe all those Li systems have a power regulator which has current limits that may not meet the specs of this project.

Markus, as stated, I was "guesstimating" worse case scenarioes on current draw. All I could find on Hitec 5925s right now was 190 ma draw at no load. But I'm sure this goes way up with a heavy load, and probably goes to a few amps if stalled. Regular servoes don't go as high, but that's the point of going digital: holding power means high current. Multiply this by 8 and add the load of the other equipment and 30 amps peak doesn't seem that high for worst case. Please get a meter in line and get some real life measurements to better estimate battery needs.

If weight becomes a problem, I'd look at nimh batteries next ( www.radicalrc.com ) . They have a higher power density with slightly more internal resistance ( less max current capacity ), but big nimhs should still be able to easily do 30 Amps. I'd stay away from lithiums because of the added regulator and current limits; some of these systems just shut down the battery if the current limit is exceeded ( crash! ).

What interference ?!?!?! Man, you've got 4 sparkplugs! Depending on the ignition system, you've probably got 20 to 50 thousand volts jumping across an air gap. Can you say "make my receiver do the jitterbug"? Does the PWM control the sparkplugs at the turbo? If so, is the signal opto isolated? Are the spark plugs going all the time or just at startup. If you can do it, don't have any wire going between your PWM and radio and the spark system.