Dave,
I asked the same question of JK when I saw that he was using a .456 lift lobe on the Boss9 with the manley spring. Theory says thats .798 lift on a spring thats "recommended" for a max lift of .750.
John actually sent me this email back
"John, we normally run the 221443 spring with .456 lobe lift and 1.75 rockers. The spring coil binds at 1.140". The actual lift will be around .760. (with lash & deflection). I ran this in my Enginemasters Boss 511 and it worked fine. The math says no but in reality it works. The closer you get to coil bind, the better the spring works.
Not To Worry!, Kaase"
The maths dont work but he is the man.
Still , I am playing safe initially with My setup , a .440 lobe , and creap up on the spring by tightening up the lash?
John.