pushrod length ball to cup

Does anybody have experience with 400 pushrods length for hydraulic cam and adjustable rockers? What length pushrods do you guys have?
Is stock adjustable size 8.250"?
All the lengths I had on mind are:
8.250" = 20.955 mm
8.291" = 21,059 mm
8.300" = 21,082 mm

This means that the longest and the shortest are less than 1,3mm different... Can it make a dramatic difference in this case?
Perhaps I'm overreacting with this and should just go with any of these?

Are rocker stand shims a way to optimize geometry with these small differences?

Sorry for my perhaps very basic questions, I'm new to this and this forum is a place with so many experts that you are prolly bored answering this sort of questions to newbies...