For “C” races we don’t taper at all.
For a Sunday “C” race, I recommend doing your long ride on Saturday before your race.
If it is a running race, skip your next scheduled run, then do easy recovery runs until you feel recovered.
If it is a combo run, bike race, then skip your next scheduled run and make your next bike an easy recovery spin. Continue with recovery workouts until you feel recovered.
For a Saturday “C” race, I recommend doing your long ride in the middle of the week if your schedule allows (or try to make your other aerobic ride longer if possible). Then do the race in place of your Saturday workout. Then recover the same way you would for a Sunday race (see above).
P.S. Always wear your HRM and use all your gadgets (power meter, garmin) for these races since they give us valuable testing data!