Not to seem argumentative and/or rude although I have no issues with being such, actually I do realize how it works; you are the one not understanding how the duct pieces work. The ducts serve to direct the hot air up and out of the vehicle rather than blow it toward the fuel tanks and around the engine compartment which would interfere with their performance. The boxy end of the space will create vortexes trapping some of the hot air.
I can see the kit instructions on my screen right now: the ducts come down and pretty much mate up to the radiator. There is no appreciable ‘side’ from the outer and inner hull plates to act as ducts; only the actual duct is filling the space. And while not ‘tank coverage’, the ducts do cover the tanks from view as they sit between the tanks and the exhaust grates from the vantage point of someone standing on the engine deck and looking down.
You aren’t the only one who has seen things first-hand; David’s web site is full of articles where he made his own measurements. He doesn’t spout nonsense or he wouldn’t be tolerated here and no one would heed his advice on the topic.
I happen to be familiar with German air-cooled engineering having owned and performed maintenance on various vintage VWs of all types, as well as the occasional Corvair.
I also can gather evidence to support the function of the parts represent by J6 and J7, but I don’t need to because I believe I know why you think you see what you see.
You saw a Tiger that was missing the ducts.
And while I was writing all that I see you submitted a response. Not meaning to pile onto you, but that really just took looking at the illustration a little longer and the connection to how it works IRL would have kicked in.
You rustled my jimmies when you took on Mr. Byrden, who I feel has earned a reputation for his work on the Tiger that benefits us at this site.