When I bought my
Boler, the curtains were hung in curtain rod brackets that looked so beat up that they could have been original. They were riveted into the metal frame of the side
windows. The curtains hooks at the front and back
windows were definitely add ons since they were poked through the shell. I installed a small storage unit at both the front and back to allow for a metal curtain rail to support the wide expanse. My side
windows since I installed newer and bigger windows have medium screw-eyes with a metal curtain rail which are screwed into the new wooden window trim.
Don’t be afraid to poke holes in the shell to mount a decent bracket. Just make sure that you do the marking work from the inside, drill from the inside [use a soldering iron to melt through the elephant skin or a slow drill so that you don’t twist the material], use 5-minute epoxy to seal the hole as you insert the stainless steel rivet through the skin and through the bracket you are going to install [stops the rivet being an entry point later], pop the rivet and then using an acorn nut finish the inside installation to hide the unsightly rivet.
Always use stainless rivets since there are fewer problems with metal to metal corrosion and rust.