i gotta say, as i looked at it in the light of day the next day, the finisher has transformed the rear end of my civic...classed it up a whole lot. the pix don't do it justice. extremely pleased with this little mod.
mine is oem, and it is oval. my stock tailpipe was too large for the adaptor, so i just drilled two holes to attach it. very easy. you're right, oval looks better.