In reply to Scoobied64:
Done a couple of these now.
Get some tantalized timer and frame around the full container obviously not the door.
Then screw panels to these.
Leave a gap at the bottom and use marine ply or at very least resin coat or weather proof the plywood panels.
If you use 4 by 8 ft panels, put the timber so that as the panels join the uprights are a joining on both.
Leave slight gaps between panels to allow for expansion and use decent screws that wont rust.
When fitting t-nuts use screw ins not hammer ins as if one pops you have to take full panel off to replace it.
Finally weather proof the gaps at top of wall/container. Don't completely seal as the container will expand/ contract anyway so will create gaps.
And lastly if your as OCD as me get holds that are UV resistant as they will all fade at different amounts and don't use black paint as it gets to hot over summer.