… that makes sense. Mine is quiet, so don’t really know what else to chase for you, other than I’ve reversed the rear window seal and eliminated the chrome press in thingy, which may be a tighter fit? Dunno.
Edit: I happened to just watch the YouTube Built by Many episode 1? 2? (I need a life, I guess), and noticed that he was driving SNG’s hardtop equipped OTS which was quiet like mine… so looks like it can be done, and it’s not just the luck of the draw.