Sharing some of my recent experience. Biggest is settings on the john Deere 8300 grain drill. I couldn't find anything on settings for sunflower.
The planting rate for drilling sunflower was 4-5 lbs/acre.
I started on a setting of 14 and quickly realized that I was putting about 10-11 lbs/acre.
Got a really thick stand but the heads are about 1/3 the size of normal.
I adjusted to a 7 and soon realized that was too small of a gap and it was grinding a lot of the seed.
Not enough plants but huge heads.
Opened up to a 10 and got great coverage. It put out about 7 lbs/acre with very consistent coverage.
I did see the value of pre-spraying with roundup.
I missed this area and all my sunflowers were knee high with silver dollar heads.