The lash problem has nothing to due with overlap, although there is overlap in a CS cam. Every revolution of a CS type cam the direction of force on the teeth changes 6 times, pushing the valves open and then the springs pushing them shut, same with the fuel pump. A small amount of extra lash multiplies the excelleration, aka gear bang by many times. Extra lash is what breaks the gears, not inferior gear metal. This problem exists in the Lister built engines also. I have one in the shop with gear issues and it sure isn't the first one.