I just took a look through the Shell Racing Annual for the '68 season, and Robert Stewart actually finished runner-up spot in the 1001cc - 1300cc class behind championship winner Angus Hyslop, and he did seem to race at every round. He won four races, and dnf'd just once. Collins raced his PDL Mini in the 0-1000cc class, finishing 3rd, but he seems to have suffered a bit from unreliability in the latter half of the season.