Kyle,
start out slow and simple with things
filler metal goes with base metal, good start
now for some questions
welding process? gtaw gmaw saw, etc etc?
manual or robotic?
what is the tube shape? ie square, rectangle, round etc etc
1/8" gap for 1/16" thickness seems alot of gap to me
I think I have done what your describing here
but need way more info to help
sincerely,
Kent