Where I work we are required to weld both uphill and downhill vertical with and without a backing strip. You will find you will need to turn your voltage and wire speed way down when running uphill. For instance on 1/4" running vertical downhill I run at 26 volts 550 inches per minute. For the same weld going uphill I will run 23 volts 175-200 inches per minute. The recently required us to run uphill on material as thin as .143
Most of the guys thought it couldnt be done, however, if you set your machine correctly, the weld will pentrate completely and look very nice.
Dont forget to try different methods of movig your puddle such as an inverted horshoe pattern ,looks kinda like "U". One of the new methods they are teaching at the local college is a triangle pattern. I have tried them all including going just sraight up and I prefer the horshoe. Its up to you,try different settings and methods until you find one that works for you. Good Luck