Flight Test Required
You need to test to determine static source pressure error for your specific airframe. It's a 3 step process covered in previous threads: ground test (leaks/ASI error), flight test (low/fast "coarse" check, GPS runs at multiple altitudes "fine" adjustment), and data reduction. Wash, rinse, repeat if you make adjustments.
Basic installation per plans generally gives good performance. Proper pitot/static flight test is tedious and can burn quite a bit of 100LL to really dial a system in, but unfortunately, every RV is different, so there isn't a set of standard data.
Drop a PM or email, and I'll share a spreadsheet that can help with data reduction or answer your questions if you decide to test after you've reviewed the previous threads on the topic.
Cheers,
Vac