3 piece suit source?

[Mikilt]

I found a perfect three piece suit at a Goodwill store! Perfect except that it doesn't exactly fit. As a Gentleman of Substance, I am accustomed to working around "fit issues".

I am making a new back for the waistcoat in order to allow it to button in the front.(A difference of about 7 inches) The sleeves and shoulders of the jacket are okay, but there is enough seam allowance for me to let it out a little bit.

The first time I did a jacket conversion, I cut the jacket too high - at the hips. After studying pictures of the Duke of Rothsay, I have cut this jacket about mid-rump. I tried it on and looks and fits great.

What's the secret to getting smooth curves on the sporran cutaway?