Bud Vase Bracket Placement

[Jim Kroeger]

I know there is no rule about where to mount a bud vase in my 30 Town Sedan but what I want to know is what do you screw this into? I would like to place them behind the rear window in the sedan in the curve of the body. It seems this is some type of pressed board behind the fabric but how thick is this board?. How close is the metal of the curve in the body next to this board so I know how far to drill and what length screw should I use? Any ideas? Thanks. Jim