Custom Tubing question

quick question - im thinking of making my own rear brake stay & top motor mounts out of some tubing. im kicking around the idea of using old table or chair legs (chrome tubing) or maybe shopping cart frames if theyre strong/safe enough. if that stuff is too weak i would maybe try some real tubing from the metal supply place.

anyhow, i was wondering how to crimp down the ends so they look nice & not all mangled. some of the pieces ive seen, where it goes from round to flat, at the end of the round part, it has a nice curve & then a sharp transition from tube to flat. the flat area would then be drilled out to use for whatever i need it.

anyone ever do this or is it a bad idea? just trying to think outside the box.