Hi Paul. Photo does not show much but all I've done is bend two 3-4mm ally strips, about 4 cms wide, into U shapes. The bottom half of the U screws onto the wooden batten on which the spare wheel bracket usually mounts and the top half of each U has a stainless M8
rivnut which the panel just fixes to with stainless M8 allen bolts. A certain amount of experimentation/bending is required to get the rivnuts to just the right level. Hope this helps.