The GC7 is def slower and banks longer than a brand new Diamond 9’. The GC7 is proper.If it is the exact same cushion as Diamond then being slightly higher could be the factor in slowing them down - IDK as I am not a physics guy - but the GC 7 that I played was recently installed by a known excellent installer. It had the Simonis 860 so comparison to a newer Diamond - the GC cushion was slower on rebounds for sure.
I only got 4.5 cushions on a solid hit up and down the table/ a newer Diamond gets 5 minimum in my experience.
My own GC 3 with new Simonis 860 and newer superspeeds gets 4.5 cushions up and down.
I took a 3D printed ball with a flat base to the expo and marked where it touched the cushion on both tables. The GC7 was about .75-1mm higher. (.030” - .040” or so).
I talked to the Brunswick president about that and he said something to the affect that it was on purpose and Gregory did the rail design.
I asked Gregory on FB a few months back if the cushions are exactly the same. His answer (me paraphrasing) was he was not at liberty to discuss those details as it’s not his company.