Dimple dies

[pressbrake1]

That's the best way to do it.
You can get the exact profile you require then.
The ready made ones are fine but give a different shape of dimple depending on how they are made and how thick the metal is.

Buying/making a matching set gives you the most chance of all the holes looking the same but if you put a 50mm dimple into 1mm and 2mm sheet they won't quite match.
You could also make them to match whatever hole cutting tools you have.
I bought a set but they (like most) were imperial sizes so I had to invest in some imperial hole cutters as well!
If you have the stock, a lathe and the skills then make them up.
Unfortunately I only have 2 of those 3 things!

I make hydraulic rams so Ive got a nice stash up to 200mm diameter

 

[excossack]

Maybe I should have gone the mesh route, you live and learn. I think I underestimated the weight of the metal once all welded up.

 

[hotponyshoes]

Depending on how much load you are putting on the shelf you might get away with just cutting the holes and not dimpling them,
Get a 1" and 2" hole saw and go through the box and the sheet.
If it does go all floppy you could still get some dies and dimple afterwards. I expect you could drill out a third of the weight and if you stagger the holes you might not weaken it that much.

 

[excossack]

I was thinking of the hole saw route as there is a good amount of stiffness in the metal work now.