My question is inspired by charlieman's (awesome!) thread, but is not meant as judgment or veiled criticism. Just an honest curious question: For those of you that do safety-critical major fabrication like frame building, how do you get comfortable that it's safe?
Presumably a one-off home project doesn't get dynamic stress modelling; engineering review; destructive testing; weld inspection; etc, etc. Is it experience based on doing similar work professionally in day jobs? Comparison to other manufacturer projects? Road testing after it's built?