it's really going to be hard to guage these. just because you have a strong extension doesn't always mean you have a great bench. and even if you have weak extension you might not have a shitty bench. even more, people do extensions differently. some guys are doing more of a JM press or they are bringing the bar down and touching their chin to it. this last one is the way i saw dave do them. there might be another guy who is holding his elbows one position and lowering it to his forehead.