The welder worked well, I should have had a bit of practice before I started as it's been a while so I had to redo some welds but that was my fault. The best thing about it was I could weld all day without hitting the duty cycle, it had no problems with the 6mm or 4mm and you can see the heat marks on the back of the pieces showing decent penetration.
If you look half way down the front face you can see where I had done some stitches of the 6mm winch plate to the 4mm face, when I'd done the whole thing you could see all the weld lines on all pieces
I ran it on some 3mm as well but haven't gone any thinner, I'll see if I get a chance to try it on some real thin stuff this weekend.
Cheers
Steve