I don't know if this is necessarily a good approach. I haven't actually tried it yet. I bought a thrift store jacket that I intend to convert to a Prince Charlie. I have read the threads that say such conversions can turn out wonky, but I am going to try anyway.

As for the waistcoat, I am a gentleman of substance and the jacket doesn't fit me in the waist. I intend to follow the lead of my local kilt rental shop and "sew in" the front and lapels of the waistcoat. This should give me the look that I want with the fit that I need.

I am not sure how I am going to do this yet. Perhaps I will cut out shapes from newspaper pages and tape them to the inside front of the jacket until I have the shape that I want, then use that paper as my pattern/template.

How will I know which shape is the correct one? Google Image search.