I give to you all the soon to be infamous Double-Helix of Doom:

This one would use Grid Configuration "A" in another topic.
I'd like to propose the following if we get > 80 cars:
4 Run Groups by Class. In the following table H is for Heat, W is for Work, and R is for Race.
H W R
1 A D
2 A B
3 B C
4 B A
1 C D
2 C B
3 D C
4 D A
In this example if you work Group A, you run heat 4 in the first and second set. Or if your car is in Run Group "D," you work the final two legs of the second heat. In this setup there is always time for you to break away. Workers in Groups C and B have a tricky worker/driver swap but only once. The sessions would be quicker (fewer cars) and the worker rotation (4 instead of 3) would be easier. In an 80 car event this would equate to 15 workers on average: 1@Grid, 1@Entrance, 1@Start, 3@Trailer, 3@C1, 3@C2, 3@C3.
With 100 cars, it becomes even better. With 70 or fewer cars, we can afford 3 run groups as before.
The "3 Corner" assignments would be in a "V" Position: upper LH Corner, upper RH Corner, Lower Center. If needed, the 4th corner could be upper Center.
4 runs in the first set of heats, 4 runs in the second set of heats, 8 runs total. Make time for fun runs. Cash is King.