Agreed, unfortunately the car is having the complete interior redone at the moment so I don't have access to it. I need to purchase the speakers and send them to the installer.
Problem with mounting on the shelf is that you have to use external enclosures, so it's not going to be a "clean" install. The shelf doesn't have much depth beneath for a nice flush install. (I was hoping to do that at one time, but was disappointed as to the reality.)
I had trendy (in 1977) "ball speakers" on the rear shelf of one 308GTB and the placement by your ear is VERY tiresome... Renew the door placement and add a tweeter pointed off the windshield.