My new chassis build

[Talonmotorsport]

I would say go for 2mm ERW as it's a nicer material to work with, just remember to grind a 1mm 'weld prep' (45' angle) around the edges. This will aid in the finish weld as it will give you a guide so you can see the joint,give better penetration in to the material and also means there will be some 'meat' left if you grind the weld nearly flush on the out side to fit the panels.