Yeah, 10% (if they actually lose that much) is only 14-16 pounds so it’s not that critical.
Of course, being the anal retentive simple minded fool I am, I’d measure the springs after break in or maybe after dyno time or several hundred miles and shim them.
The 14-16lbs reference puts me in or knocks me out of the 145-150 & the 350-360 ranges. I know that I am being anal about it, but if I shim for the ranges and the springs do lose tension, then I am under the range.
If I compensate for the 10% loss and they don't lose, then I am over the ranges recommended by the cam guy.
GRRR: I don't want to invest into a spring checker.