1.6mm mild steel will be pretty dent resistant without worrying about heat treating. We use that for top sections of our medieval combat helms. Using heat treatable steel such as 1050, 4130, 1095, etc allows you to use much thinner steel for the same strength. I'm going to try and form the entire top half of my Mk Vb out of a single piece....we'll see how that goes! Lots of intricate lines and small details, but I have a crapload of steel forming stakes. Whether or not I remember how to use them after 20 years remains to be seen!
You're off to a great start. Nice symmetry and clean welds! I'm looking forward to seeing the rest of it.