I copied the official MAAC Rules for LA 25 Sport Race.
G.3.16 LA.25 Sport Race Rules
3.16.1 Purpose: It is the intent that this event will provide the competitor with a racing event which is low in cost, and fun to fly while providing a good training ground for those who wish to move on to more advanced forms of racing.
3.16.2 All pertinent M.A.A.C. racing rules shall apply in regards to safety and conduct of the races, except as follows:
2.1 Engine. The only allowable engine shall be a commercially available and absolutely stock OS Max LA .25 engine, operating on suction feed. (No chromed liners, or modified piston/liners will be allowed, and only the standard LA.25 venturi can be used.)
The only allowable modification is the replacement of the plastic backplate with a metal OS or Thunder Tiger replacement
It is recommended that all engines be checked before racing commences, and afterwards at the Contest Director’s discretion.
2.2 Aircraft. The model must be of profile fuselage type and have minimum fuselage length of 24 INCHES when measured from the face of the thrust washer to the leading edge of the moveable elevator.
2.3 Wing. The model must have a minimum wing area of 300 SQUARE INCHES and a minimum thickness of 1 INCH when measured at any point along the span with the exception of the last 5 INCHES before the wing tips.
2.4 The model must have a fixed landing gear with a minimum of one wheel not less than 2 INCHES in diameter.
2.5 The model may be equipped with a fuel shutoff system.
2.6 Fuel Tank. The fuel tank shall be fully external, mounted forward of the leading edge, and located on the outboard side of the fuselage. The tank may not be designed to cowl the engine. All vents are limited to 1 / 4 INCH outside diameter. The tank may not be pressurized but the vents may be directed into the airstream.
2.7 Propellers: Only stock black Master Airscrew 8 X 6 props will be allowed. (Only balancing and the removal of flash will be permitted.)
2.8 Fuel: Commercially available 10% Nitro Fuel will be used in official racing, and this will be supplied by the host club, at a nominal cost, in pre-designated containers.
(The fueling of models will be monitored by the race officials during the race. Immediate disqualification will be the penalty for any team that substitutes the official race fuel for their own.)
2.9 Glow plugs: Any standard glow plug that fits ¼ X 28 NF threads will be permitted. (Modified threads, or clamps will not be allowed.)
3.16.3 Prohibited Equipment: Pressure re-fuelers, hot–glove electrical contact systems, and centrifugal carburetor switches are prohibited.
3.16.4 Pull Test: The plane and control system shall undergo a pull test of not less than 25 pounds.
3.16.5 Lines: The minimum line diameter shall be .015 INCHES, and be of stranded construction with a length of 60 Feet plus or minus 6 INCHES when measured from the inside edge of the control handle to the centre–line of the airplane. Mono–line systems are not allowed.
3.16.6 Races: Preliminary heats shall be of 70-lap duration, with one pit stop required. Two preliminary heats shall be flown with the best result to count. Finals shall be of 140 laps duration, with three pit–stops required. All races shall be run with at least two, but not more than three entrants.
6.1 The start of a race shall begin with a two-minute warm-up period. During this period, the engine can be started and run right up to the commencement of the race. (The engines need not be shut - off prior to the start of the race). The starting signal shall be by flag, whistle or other highly audible or visual means. Once the signal to start has been given, the models can be released by the mechanics.
6.2 In the event that a competitor’s model completes the required number of laps in a race without completing the mandatory number of pit stops, he will then be timed until he completes the required pit – stop(s) and then flies one extra lap afterwards.
3.16.7 High Flying: The Contest Director may assess a penalty of two laps per infraction, and his penalty will be added to the length of a heat or final in which the penalty is awarded. Normal flying height will be between 10 and 25 FEET, except for passing.
3.16.8 Safety: All pitmen shall wear a hockey or motorcycle type helmet, which provides full coverage for the sides and rear of the head.
All pilots will fly without caps/hats to avoid the lines from catching on them. No water bottles will be allowed in the flying circle.