Valve Spring Question: Coil Bind Versus Spring Quality

I am looking at two valve springs for a possible upcoming cam swap. This will be for a solid flat tappet that will max out around the 6300rpm range with 1.65 rockers.
Note: I have been told in the past that the 1.65 rockers will need a little more spring pressure versus the 1.5 rockers.


The two springs that I am looking at are the Isky 6105 and the 6105SP (SP = Hi-Tensile chrome silicon outer spring, Spintron proven up to 8000rpms).

Question 1: Is the 6105 spring a good spring choice up to 6300rpms?
At my installed height, coil bind clearance for this spring would be about .080” at max lift.
Spring Pressures: apx 155lbs & 331lbs max lift

Question 2: Is it worth it to buy the 6105SP upgraded spring (+ $48 per set) if my same installed height coil bind clearance would now be in the .140” range?
Would the better spring material hold up at the higher coil bind clearance?
Spring Pressures: apx 163lbs & 361lbs max lift
Any issues running the 163/361lbs on a solid flat tappet? I just pulled out a solid flat tappet that I had setup apx. 149/365lbs with EDM lifters and the cam/lifters looked good, but with very low street miles.

I have talked with three cam vendor's and they all suggest something different for their version of a solid flat tappet spring pressure with EDM holes:
a) 135lbs/360lbs
b) 145lbs/365lbs
c) 130lbs/340lbs MAX!


Thank you!