VCMC club manages about 800 runs in a day, but heats don't get to run twice in the day. The 130 drivers get their 6 runs and work and that's it for the day.
Close....but not quite
I can provide some insight on the Pitt Meadows events. Seems quite comparable to where you guys are at.
VCMC caps their events at 140, but are usually in the 100-120 range.
UBC caps their events at 80 + the organizers. They usually sell out quickly and are in the 90 driver range.
All the clubs (assuming 80+ drivers) have 3 run groups, no lunch break, and have 5 or 6 work stations with 2-4 workers per station. It's common practice to do 3 runs for all 3 groups in the morning. Then they evaluate the time taken and adjust the afternoon runs accordingly. With 90 people we usually get 4 or 5 runs in the afternoon and 120 people will get us 3 afternoon runs. Typically running from 9:30 am until roughly 4:30 pm. If we're closer to 80 drivers that means that some people - timing, chief of workers, grid, etc - might work more than one heat.
Course overlap allows for barely 3 cars on course - really only 2. Meaning the 3rd car is released as the 1st car finishes (with the 2nd car mid-course).