I used 2 lengths of 9.5mm aluminium angle cut to about 5mm shorter than can size. then 1 lenght slightly bigger than 3 can widths.
Then 2 lengths of 10mm flat aluminium to make the frame, one either side of the angle and bent another length of aluminium angle round as the surround.
I filed down the bolts on the reverse side to the same thickness as the flat aluminium (about 1.5mm) for a stand-off. I have just glued it together for size but will bolt it down once i have the shape right (as you can see the surround is a bit skew wiff). I will use a pin sticking out from the hull with split pin for the surround ends so it can be taken off
I had seen a similar system on some historic photos. The cans sit on the angle and are held by the surround strap. Simple but does the job