As Sev says light carries far further than sound and much faster especially in the dark months of winter or a night time operation which would have been rare in WWII, one flash from your exhausts and the game is over, I would imagine that the vents in the side are to allow air into the extensions to help burn fuel vapour don’t forget you need oxygen to ignite fumes in all that carbon monoxide, as for the top well there are no pictures so again we will never truly know but I would go with the Panther type fans as it sounds and looks more plausible.

10/10 for a truly unique build one which only a truly dedicated person would follow