Hi Serge, you are over thinking and over prioritizing this entire Peacemaker project.
First of all this model was designed as a combat/sport model; it was supposed to fly
competitively fast in those days. It was intended to fly on 52' lines. You can slow
the apparent speed by flying on 58' - 60' lines. You can use any of your 5.5-6.0 oz
engines. You can even use a baggie/balloon tank if powering with your Cox Olympic .15;
which will give excellent fuel feed resulting in constant engine runs. DO NOT move the
CG any more than 1/4" forward. You've already been given advice about elevator deflection.
Another thing to consider when flying CL models with "Combat" sensitivity, is to narrow
the line spacing on your handle; these models respond instantly to control input, far, far more
quickly than a "normal" stunt model. Flying this model will reveal where you want the CG located,
and just how much line spacing you want at the handle.
One last thought, just because a Combat model can change directions so quickly, this does not mean
that the model is in an unstable trim condition. Combat flyers spend a lot of time in the circle NOT looking
at their model, they learn to feel what it is doing, this involves the stability to fly straight out of popping
a 90 degree turn, this requires a very stable straight tracking design.
I'm guessing 58'-60'line length and an 8 X6" prop will give a comfortable and confidence inducing flights.
Good luck Serge;
Tony