I am planning to fly speed limit at the Nats this summer.  It says slow combat rules with a 75 mph speed limit.   What aspect of the event 329 are being adopted?  Strict 329 rules have mandatory fuselage dimensions and no pressurized fuel systems.   I guess I would like to know exactly what the rules are that will be flown, so I can prepare properly. My speed limit airplanes do not meet the 329 criteria.