If i may, I would like to suggest quite a few yards/meters of practice beads might be in order, specially for a suspension piece under great loads and stresses.
You need to learn penetration ( sexy welding talk I know!!! ) heat settings, gas flow, pull or push, tip angle, wire stick out, proper puddling, warping, single or double pass (with a 135 ) and wire size off the top of my head. MIG is forgiving but why push it. Oh and getting used to your helmet also takes time.
I would get scraps of steel about the same thickness and practice your welds, cutting through the welds to see penetration, shielding and heat indication. I bought a couple of books that show what a good bead looks like and that helps a lot, one being by Miller.
I practiced for a couple of weeks on all sorts of thicknesses before I felt comfortable enough to trust my own welds. Good grounding and really clean surfaces are a must!
What ever you do, good luck and take lots of pics for us.
Pierre