Box is on it but... What version of SketchUp are you using? Your profile indicates 2014. Is that correct? I don't believe the inscribed/circumscribed option had been introduced yet.
Just had a very quick play and I think it works pretty well. Of course once you have the scene you can turn off the W/mark and merge model and photo post-pro.
Well done for the question, having the same problem myself, you got me thinking...
... would love to see how you go...
ps: this a direct from SU image export.
Pavillion curved roof-working.jpg
