Hallett Race Formats

What is the format for the races this weekend? I note there is no qualifying on Sunday and recall reading something posted about R3 & R4 grid positions yada yada something like nationals. I couldn't re-find it.
R1 - based on qual
R2- invert of R1
R3 - ?
R4 - based on cumulative of R1-R3 points? Summer Shootout Champion

I've never been to nationals so I don't know how its done there either...

Last year (and I think the year before) it was...

R1 - based on qual
R2- invert of R1
R3 - invert of R2
R4 - based on cumulative of R1-R3 points - Summer Shootout Champion