A reason why other than binding on the way down , which would'nt have the detrimental effect so related to lash as the "closed spring tension" and @ height of said spec - is not kosher to setting lash spec . ie. closed they sit too tall or too remotely possible supplied retainers achieve out of spec height and similarly not in the ballpark for std. adjustment procedures . Inferring that geometry -" can't get there from here ".
I know that's not a solution , but be wary of tips that "can MAKE it work" , get second opinion , hopefully someone has real experience here specific knowledge , beaucoup "builders" on this site , ya know. And tapping another mach shop w/exp on that motor and /or Kelford specifically most valuable too ,see what they say.