This may be a stupid question, but when an external control system is used on a combat plane (typically a foam wing), is some adjustment required to keep the outboard tip from flying high upright and low inverted since the leadout guides are above the vertical CG?  Or is the distance involved not enough to cause a problem?  Or none of the above?

I have a couple of Russian Fast ARFs (older ones with the square wood boom) that I would like to convert to .20-powered stunt trainers.  I would prefer not to cut into them, but to attach an external bellcrank and external adjustable leadout guide.  The stock controls are made for a short lifespan in combat (hopefully these won't die TOO fast!) and the leadouts are too far back for stunt.

Thanks,

Thanks, Ken.  Yes the Sullivan Nyrod trick would work since the plane's roll attitude is determined by a line running from the leadout guides at the tip thru the vertical center of gravity midplane (when viewing from the front or rear), regardless of the bellcrank position, which a lot of people have trouble getting their minds around.  It is kind of weird at first.

So if I wanted to use external controls on a built-up ARF wing converted to stunt, I would probably have to make it a kind of high-wing profile (controls on the bottom) with the engine center line and everything else lower than the wing centerline, to move the vertical CG down.  Sort of like an Old Time Boxcar Chief.   

Hi Kim,
I like the above approach - get it flying; It'll probably be fine.  Then trim using simple adjustments.
That said... 
How are you mounting what I assume is a plain bearing .20 in the large space meant for a BB .36? 
If you go with external bellcrank, you might have the option of mounting the engine off of the center line, vertically  --- moving the vertical CG closer to the level of the leadout guide.  Extra benefit:  If the controls are on top and the engine is slightly raised, you should get less dirt into the engine on landing.
 Re: Engines -- Are you using the rare and coveted OS fp20?  I'd use something like a LA25 that is currently on the market.  Save those fp20's for the stunters with landing gear.  Or use a pb .40 with a small venturi?

Rambling .... sorry.
Randy