The conversion from CL to R/C on the Stearman... use the smallest engine in the recomended range. It will be PLENTY.

The C/L planes tend to be lighter than R/C planes, and the control movements tend to be HUGE So make sure you reduce the elevator throw vs recommended for CL.

Not ALL biplanes are bad about stability... The Tiger Moth for example is just as good as a Piper Cub for use as a trainer.... maybe better. A Tiger is noted for being EASY to fly, but will show you your errors in a manner that doesn't tend to kill the pilot. Pilots trained in Tigers could move directly to a Spitfire (a notoriously touchy plane) with little to no problem. The scale models of Tiger Moths seem to have generally inherited ALL of these qualities from the full scale aircraft. (DeHaviland knew how to design GREAT aircraft.)