You can't just measure this up in CAD? You seem to be pretty proficient in it. Think about what Jon said..
I need to send you an email anyway..The way i do it is I model the rocker arm and put it in a number of assemblies that can be viewed all at the same time, each at a different lift, say 0.050" different.
Then modify the shape on the rocker arm until the contact points and entrainment velocity works out.
If someone spent the time to figure out the relationships, it could be coded in a day or so I guess.