Judging from the streamers, Id guess just after a mid air...

The first combat spads we flew at our club were .40 size spads we down loaded off spadtothebone.com. I built a 48" Devistator v tail rig and a few other variations of it. If you go to the spad forum there are also links to plans there. I started out with a K&B 65 on mine at about 5 pounds. It was very fast. We eventually went to more standard nimble .25 size planes though we do still fly open C rules at club events using .40-46 size engines once a year or so. .40 size or less is good guideline, we like the 40 size combat cause more people here have old trainer motors lying around than .25s.

Have fun and be safe, combat adds additional risks due to the nature of the game.