Hi Flicka: Most bipes, in my book, do not have anywhere near enough vertical tail area, resulting in nasty handling anywhere near stall. The airflow over the tail feathers of bipes is messed up a lot more than that of monoplanes by an extra wing and its cabane struts, and the lower reynolds numbers of models worsens this nasty effect. The best cure for this is to enlarge the vertical tail area. I like to give the fin and rudder at least 15% of the total wing area, for non-scale designs with normal layouts. The Ultimate is a good example of a bipe with enough vertical tail.

The simplest way to try out a bigger vertical tail is simply to tape a cardboard extension to the trailing edge of your rudder. It does not need to be at all robust, since you do not need to fly very fast to determine whether it works. If your rudder authority was already strong enough, simply reduce rudder travel in proportion to the increased area. I would be inclined to roughly double the total vertical tail of the Stearman to get really friendly handling. Trying different size cardboard extensions is very easy, and can be done during a single flying session.

A little washout in the wings also helps, and beware of washin, - even a tiny bit poisons handling, and four ailerons are vastly better than two - much less adverse yaw and less tendency to bite you with snap rolls at inopportune times.

Bipes do not carry weight as well as monoplanes, but this can be overcome with more power. If you are carrying all that noseweight anyway, maybe a bigger engine would be worth trying.