Sport Coupe Rear Window won't stay up

[sinbad339]

I have a '30 Sport Coupe, and have a list of things to do during our northern Ohio winter. One issue I'd like to fix has to do with the rear window. When I "secure" the window flap up (during hot weather or with someone in the rumble seat), it won't stay up as I drive over normal road bumps. With the weight of the glass, it is soon falling down on my head.

The car seems to have the correct fasteners; three "Stud Fastener Eyelets" in the flap and three male studs that are fastened into strap fabric in the roof. These are the studs that the pin is depressed to retract a hook. See the pics below. I also checked and the hooks in the male studs are all facing forwards, which seems to be the best considering the way the flap hangs.

Anyone have any suggestions?

Thanks in advance