Good old flux core e70t-11, this is similar (I use 212mp) to the same wire I weld with at work when I am outside (and in a hurry 5/64 diameter). I always found that that wire will make a very nice vertical too when you get the heat just right. The only drawback about the 211mp you use is that after you weld (multipass) over 1/2 is that the elasticity is lost
, the 212 is good for an 3/4 to inch thickness. I have used this for piling and other structural steel with great success an I always found that the 212mp has more spatter than 211.