Hi Pooh Bear

Sure you can weld thicker metals. Metals are differant thicknesses for many differant reasons, basic shape, strength, strength over size (length), and the list goes on.
You basicly have the right idea with multiple passes. However if you are welding something for great strength a couple of things that you could keep in mind is the power of a picticular machine will only drive the moltoned puddle into the metal so deep. so if you bevel the edges of the metal you can get full penatration. Keep things really clean by grinding inbetween passes.
Another thing is your selection of rod, 6010, 6013, 7018, 11018 these rods are are designed for differant purposes and positions (flat, vertical, overhead, all positions). If you pick the right rod and the right position you should have no problems.
Hope this helps
Roscoe

Ok, great. Thanks a lot.
This makes it easier for me to pick a welder.

Pooh Bear