Just chatted to Rick and discussed what i wanted to confirm.

Being as all of the pulleys give the cam slightly different timing the timing mark on the head will never be 100% spot on, you will have to spin the cam FRACTIONALLY to get the belt in the teeth, but it should be easily visible which teeth are closest lining up

But as Christian has said, an over skimmed head will make this worse, being as each time its skimmed it makes the cams timing fractionally out.