My RV-9A drawing 3 rev R1 calls out an AN470AD-6 rivet here. Look closely on the plans, sometimes a '6' looks like a '5' if the print process is not absolutely clear.
You should have a rivet gauge that shows 1.5x the rivet diameter on the undriven shank, if not a ruler graduated in 1/32" can be used to verify the correct length.
It may be just the scale of the pictures you posted, but the rivet shop head looks over driven to me. Table III MIL-R-47196A shows a driven head minimum diameter of 0.163" and a driven height of 0.050-0.070". I think you can download this standard from Vans or www.everyspec.com