For the roof, use twist resistant rivet nuts for soft materials (aluminum) available through MCMaster plus a little sealant. Mine was installed with drilled holes and sheet metal screws and have become a source of water leaks. I plan on removing mine and installing 1/4-20 rivet nuts - that size should work.
For the ladder on the back panel, it looks like my ladder was directly mounted to the back panel. No suggestions for SMC.
Ed