I had to play with the settings on the mask to get it right. Just a tiny bit too low or high and it's really difficult to see the weld pool.

Gaz, I'm ok seeing the pool but been having a little trouble seeing the joint lines so am tending to wander off line, going to try the chalk/scribe methods suggested.

This is what make Mig dangerous in the hands of novices and even professionals. During my tenure as an apprentice boilermaker instructor I could not drive this fact home enough to the appies and a stunt I usually did was to perform a beautiful fillet weld knowingly it had not penetrated well which impressed them big time. Big were their surprise when I took a hammer and with a fast blow just knock the weld clean off:eek:
This is the very reason as a b/maker I built and welded my own chassis. Just not trust anyone with Mig.... To prove my point I attach a picture of a failed Mig weld on suspension bracket from a factory built Westfield :eek:
Lesson from this, not all nice looking Mig welds are good welds.;)

Looking at your sample pictures my advice would be that you concentrate on your speed of weld - try to keep it constant because the width of your welds shows uneven speeds. Get this right the rest will come together soon. BTW, better to push Mig rather than pulling it. Doing so you can see where you are welding and watch the pool and usually this result in "flatter" welds as well.