I placed a few short pieces of new clean Vascocel in the gap between the window and parcel shelf. It's invisible once inserted. We used it on low side pressure A/C suction lines in the trade. Lowe's has similar product.
https://www.lowes.com/pl/Pipe-insula...ing/4294765360
I used the Vascocel due to old stock from my A/C Local 146 Plumbers and Pipefitters days. Cheap.
https://www.lowes.com/pd/M-D-1-2-in-...aps/5014821845
Back in the day the mechanics would ride in the trunk over RR tracks at Broadway St. (Broadway Hotel Brothel -Wild West) when Frank Kent Cadillac was in DT Fort Worth. It was hilarious. It was a good way to find rattles. One driving and the other in the trunk with the lid open.