My leather tool box for Fatboy came with the extension and bolt. The bolt does recess like you said. The sleeve was metal, not chrome, so I painted it black. It definitely is strong enough. The pegs have to swing out side ways, not up and down. Have not had any problems and have had a couple different passengers.

 

the footpeg extension kit for the chrome boxes should fit and you can get em at your local stealer for $16

 

thanks I found them. I feel like a dumbass for not looking closer at HD's website.