Unless I have overlooked it there appears to be no way to detect if a race has compulsory stops. Could this data be added to the RST packet? There seems to be three spares bytes here and it would be an appropriate place.
struct IS_RST // Race STart
{
char RST [4];
byte RaceLaps; // see "RaceLaps" near the top of this document
byte QualMins; // 0 if race
byte NumInRace;
byte Spare; {*** COMPULSORY_STOP flag ***}
char Track [6];
byte Weather;
byte Wind;
byte Sp0;
byte Sp1;
word VerifyId;
};
