The threaded inserts on the Rad racks are put there by Rad to mount one of their proprietary small or large baskets (more like cages) or platform.
MRI-Denver then offered their 3rd party Rad spare battery Carrier and Topeak MTX bag mount adapter to fit the Rad rack threaded insert pattern.
It should be relatively easy to fabricate a wooden deck like on the RadWagon, countersink, four mounting holes and attach it with M5 x 0.8 flat head screws.
MRI-Denver then offered their 3rd party Rad spare battery Carrier and Topeak MTX bag mount adapter to fit the Rad rack threaded insert pattern.
It should be relatively easy to fabricate a wooden deck like on the RadWagon, countersink, four mounting holes and attach it with M5 x 0.8 flat head screws.