Trick Flow Heads: Conflicting Info on Mechanical Roller Spring Pressure

To the op.
Howard's told me their rule of thumb on Solid Roller cams is,
100# per .100" of lift
So that's right where your at 660#
I used the pac 1225 spring
@ 2.000" installed height
It has 250# on the seat
And 675# open
With a .660" lift cam (after .020 lash.)
After a few runs they faded between
10-15#
Still turns 7,300 rpm for miles.
( Circle track. )