If memory serves me right, each shim just has to be leveled with the right side of the arm for each rocker arm.
There's a bunch of crazy things you can do like the mazworx valve stem conversion, idea behind is that less mass = less force.
I have not had a problem with my built head. But I'm not running anything crazy... I hit the rev limiter quite a bit also.
Super tech beehive dual springs [email protected] with titanium retainers.
Super tech valve stem seals
Hks 264 step 1 in/exhaust
Nissan oem valves
Nissan oem rocker arms
Valve guides re-sleeved with liners
3 angle valve job and shimmed with Kent Moore plate.