Bill that may be a tough to answer. The Killer Bee even though it may be cloned should still be quite a runner. I would say pretty close to TD performance. I would say it would do great on a plane that likes a bit of speed such as a Flite Streak for instance. Cox engines unlike modern engines seem to be very happy using the Cox 5x3 rubber ducky black props. These props seem to just have the proper diameter and blade area. However, I use a APC 5x3 for flying my Jr Lightning Streak which has a modified Sure Start with some Killer Bee similarities. You do need to get used to the $4 price tag of the APC and the fact that they break quite easy which makes the Cox rubber ducky a good choice. Rather than adjust speed with the prop, I went out on the line length and let the engine sing were it's happy. I'm flying with 42' Spider wire lines and the plane does just fine. I've tried several APC props such as the 6x2 which was absolutely horrible in my experience as it just beats air and allows the engine to over rev with no drive. The lower pitch props such as the APC 5.5x 2 work great for the modern Norvel's and similar engines, but they just don't seem to work well on Cox engines. The old stand by used to be the Cox 6x3 and the Top Flite nylon 6x3's which may just work well for you but since I've switched to the smaller 5" props I let let them turn up, I found that they just don't load the engine as bad causing sagging through the maneuvers. Ken