Oval career progression tips ?

I'm a road racer, i rushed to class A without a care in the world for my iRating because i only have interest in openwheel road car. (FR2, MP4).

For oval i don't have a specific goal. I have a lot of fun in oval rookie class and unless something horribly bad happens i usually finish in the top 5.

I already have my D license but i don't race it yet. When do you think i should start racing in D class ? then C, B, A, P, fame and fortune ?

The races i do in R are fairly clean when i'm in the lead pack (i usually am), i have fun and often meet the same racers.

My current standing is : Class D, SR 2.58, iRating 1557.

At some point i won't earn much iRating anymore. The high split in R seems to be a 1500~1700 SoF. Should i base my progression on iRating ? SR (which is easy to raise so ...) ? Something else ?

I'm a super safe driver, i don't go 3-wide, i don't race for the win, i race for the top 5 if able and don't mind if i can't ; as long as i cross the finish line i'm happy.

Thx <3

Any interesting link to career guide or video is welcome too.