I am an average self-taught welder with a good Millermatic 200. I guess I look at things different. I have no problem with fabing and engineering and cutting to fit and fitting tubes both square, rectangular and round, when doing front or rear subframes or even complete frame from ground up. Have a 16 foot heavy duty chassis jig. Didn't alwys though. Never had any issues with even my ugliest welding breaking or cracking. My pretty welding is pretty but I can not always make it pretty as I am not a professional. I do get good penetration though and I prep metal by cleaning any rust paint etc away before welding.
No way shape or form will I trust myself to weld up a roll cage for me or for anyone else to ride in. I will go as far as doing the fitting and tacking but will not trust my welding on a roll cage. Usually you are almost as well off financially to just get them to bend fit and weld their cage in instead of going the kit route.
Ed