armchair engineering? i don't really think so there laminar. i've been a part of multiple SAE teams, and i've helped design a couple of drag frames for a friend of mine. my first SAE team i was on, i mentioned the word schedule, and damn near got kicked off!! had to learn really quick, that for parts that matter, you rely on DOM tube. it's stronger because it's cold rolled and drawn. if the schedule 40 works, awesome! but if it was my build, i'd go with DOM.
BUT, corn's builds are quite well done, so if he thinks it's strong enough, then it'll work!
exhaust looks good! what's that muffler from?? and i like the swingarm bracing. do you think it's necessary? or is it more for looks??