Thanks for the reply Gary,
I was wondering if anyone would get in the loop here.. *S
What you say is correct. I would assume sticky friction between two materials would be in proportion to their dynamic friction. However, I could be incorrect here.
I guess you could establish at what angle the sticky friction lets go and reduce the angle a bit. Then give the test piece a bump and watch to see if it keeps moving. Once you find the angle at which the piece moves down the plane at a steady pace, you have your answer.
The main reason I suggest experimenting is you can try different surface finishes and pressure loadings to get a feel for what you are trying to do. You could also try a few lubricants for additional information.
I don't believe there is a lot of magic in this process.
Best regards Gary,