On the tight end of spec would have the valves open the longest = more intake in, more exhaust out. Sounds good to me. Setting them at the loose end means having to adjust less often though.

 

My bike starts and runs better with the valves on the loose side. Why is that? It was the only change I made and when I rolled it out on a 60º day it fired up w/o choke for the first time ever.
I set the valves to the loosest spec I could get to keep from doing it as often, since I have to check them twice a year due to mileage. Not sure my reasoning is correct. In reality I've only changed shims 6 times - the intakes were first, then 7500 miles later I did both intake and exhaust because I wanted the valves to all be at the same spec. Been good for the past 10,000. We'll see soon enough.

 

I just set them loose in order to buy more time. I never really thought about performance gains, and I didn't realize that it could make a difference depending on where you are within the specified range.

 

In theory it does. In practice, it doesn't.