Amen to the "not just for light materials" I can single pass weld 1/4 plate and multiple pass thicker with my Lincoln SP125. If you aren't getting penetration, turn it up! I run mine hotter than the recommendation on the inside cover of the machine. There is nothing wrong with flux cored wire. I've used it in 1/8" diameter using two guns at about 600 amps each for build up! I weld (along with machining) for a living and know better. Don't let anybody tell you different. If you contemplate doing heavier materials, you might want to step up to a 220 volt machine. I welded hooks on my 830 Case with mine 4 years ago and they will hold anything the loader can pick. I also built a gooseneck trailer with mine. I did use a larger wire feed for the main frame, but did all the rest with the little Lincoln. Excellent little welder.
Hope this helps.
Kim