I'm having trouble with porosity. I'm doing a 3/16" deep groove weld in the flat position between 3/16" 6063 and 3/8" 6061 using a 350p and spoolmatic 30a, 4043 .035 wire, pulsing, 50 arc length and about 550 wire speed, pure argon at 30 cfm, prep with stainless brush. The surface looks fine when done welding but when I grind it flush, swiss cheese. Any help would be appreciated.