hi mark,
When the body is on you can't see the frame anyway so I guess it's just a matter of using the best paint for the job. I'm painting mine the original colour when I get round to it but that's only coz I want it original.
As for the traffic, I can't say other than all the cars I have met have been very good. Legally you can't use the c5 on the pavement unless it's a cycle patch too.