For stainless it might be a little narrow (depending on amount of stickout you need, and how hot you are getting the metal.) For mild steel, it should be OK.
http://www.ckworldwide.com/tech-3.pdf
If you think you might be having shielding gas issues, make sure you don't have excessive tungsten stick-out or excessive arc length. For a non gas lens cup I would try and keep stickout to no more than 1/2 of the cup diameter. Gas lens cup can support as much as the inside cup diameter stickout with still ambient air condition.
If you are welding in a wind or draft, try and shield the wind, close the garage door, reposition or turn off a fan blowing into your weld area, etc.
Steel doesn't *need* really good shielding gas coverage to weld OK (get good, strong, ductile metal fusion), but you sure can make those steel welds look a lot prettier if you do (IE: treat it as if it were stainless steel, use a wide cup, plenty of post-flow, avoid getting the metal too hot, etc.) It makes the different between a "dull gray" look versus clean, shiney appearing weld beads, with "rainbow" oxide film colors.
For stainless it's critical to not to let it oxidize very much, in particular you want to avoid when the metal expands with internal/porous "gas bubbles", which makes it very weak and brittle, puddle won't flow well, etc. Oxidizing stainless I can't remember really "spitting" however.
Spitting could be from some kind of contamination, like rust, oil, water, maybe even zinc/galvanized coating. So ideally try and prepare your metals to a bright, shiney, dry, and solvent cleaned state.