Patrick,
There are no "rules" just yet. The AMA and RCCA rule books have a 1/2A "Open Class" that have been published for four years. Right now we are experimenting with "limiting" the performance because we want to avoid the event becoming an arms race.
The engines in favor at the moment are Norvel and AP .061s, and TeeDee .051s. This is the first time five or more combat veterans got together to give 1/2A try. We are all learning.
The longer spans make it easier to grab streamers, as most cuts are made with the wings rather than the props. Here is the performance data I was able to accumulate yesterday:
