heatsink led build

28eb strips 4ft.
Dude on ledg says .125mm alu strips is good.
And a lad did 1.5mm sheets. Other man says 3mm minimum but didnt state what leda..

I found sheeta of 2mm aluminium cheap nearby can i use that for heatsink riveted to my angle frame?

If not thick enough can i double the sheets up? Its cheap as fook like 5dollar a 4ft sheet
As shop same size in 3mm alone is 90 dolla so if i can double it up if needed ?

Sheet or strip best? I can cut them i to strips if thats better for air?

Ive found a alluminium roller shutter door aswel which seems to be made of u shaped 2mm profiles cheap off a van possible option

And 2mm sheet