After judging the combat events at the last Nats and flying speed limit there,I have come to the conclusion that all the events except speed limit require large investments in engines to compete.  The other events have good points that look like they would be fun to fly if it weren't for the high cost.  This limits the entries to the dedicated few willing to pay what it takes and intimidates possible new flyers.  I've been flying combat since the late 50's so I'm not a spectator to the sport.  What I want to propose is an event combining the better elements of all these events.

This proposal is meant to maximize the fun of combat with low cost equipment that is available to everyone.
 
Cuts will count 100 points and kills will end match.  (The kill rule will introduce a bit of the luck factor to help even things out for the less experienced flyers.)  One point per second of air time starting at the end of launch period.

Speed limit – 75 mph. (eliminates the technical arguments of engine specifications and the high cost of super engines.)  This is an easy to judge element that can be verified with a stop watch.  5.9 seconds for 2 laps equals 75 mph on 52.25' lines and gets around the shut-off rule.  Rotational speeds will be slightly faster than the larger 75 mph combat.   

Use 52.25 foot lines as in F2D but .018 cables to reduce the possibility of cut-away.  (The shorter lines are more compatible to smaller engines and airplanes)

Any engine up to .25 displacement, any fuel system, 2 pound max weight.

Matches will have a 60 second start and launch period during which the airplanes will be checked for speed.  The combat time will be 4 minutes from the end of the start period.  1 point per second of airtime will equal one point of score.

One airplane per match is allowed.  Starters are allowed to make more airtime flying combat instead of fighting a balky engine.  To reduce the risk of the instant start and launch used in fast combat, the pilot must do the starting at all times. The flyer will only need 1 pit man.  (F2d uses 2 airplanes and engines per match and needs two pit men for each flyer)
 
Mid-air does not end match unless both airplanes are un-flyable.

Shut-offs not required but encouraged.

Bob

If the speed limit is genuinely enforced there is no need for a displacement limit.   A weight limit of something between 25 and 30 ounces would be OK.

Modeling forebad starters 60 years ago when they were expensive and hard to get.  Today's electric starters are cheap and available to everyone.  I think they would enhance the enjoyment of a casual event and also maybe prolong the useful life of engines that don't hand start easily.

In answer to Brad's points about safely entering and leaving the circle, how about this:

1. Strat the engine "off the clock" before the match.
2. No pit stops.  Just like real airplanes.  If you go down you stay down.

All of this is for a casual sport combat event, not the main feature.

 You didn't mention if this was intended to be an elimination contest or some kind of multi-round points contest.  Or a multi round elimination contest.  I always thought a real, multi-round elimination contest with the losers in every round flying off to stay in the contest would be great.  First place- all wins, second place 1 loss, third place  2 losses,  etc.  Flying off to third place would require something like 50 matches for 16 flyers.  But with fuel shutoffs required on the planes and a kill wins, the matches likely would be in the 30 second range.

You've basically come up with a set of "slow" Fast rules.  The pit crew and fast with their launch in the first second starts was actually part of the attraction.  It added a lot of drama to the start.  The kill added drama to the finish.  Ending the match when a plane hit the ground after a midair was for safety.  Planes were often badly damaged in a midair and often not safe to fly so ending the match discouraged intentional midairs as a tactic to a degree.  Putting up badly damaged planes just for air time isn't safe either.

I'd go with either the kill/unflyable midair ends the match, or cuts only/one unflyable plane after a midair doesn't end the match.  Mixing the two has undesireable results.

I agree with Paul and Brad.  Allow starters, but only if a pit crew doesn't get a fast start, they have to hand flip at least a couple of times.  But don't require the pilot to start.  It's too easy to get over excited and trip over the lines with someone running in and out of the circle.  Requiring the pilot to do the restart makes it even worse and virtually guarantees a guy having to restart will lose on air time.

You kinda have to think through what kind of matches you want to see. Short, fast, dramatic ones with a kill, or longer, slower ones with mulitple cuts.  Or maybe short, brutal matches decided by a few seconds and with both planes broken.  How the rules are written mostly determine how the matches go.