I might suggest my stocker that converted my Darne with a 1 5/8" cast off to 3/16" cast, he changed wood types and did a flawless job. He is young, his turn around time is reasonable and he is very meticulous. He has done many very expensive guns including a Bosis recently.
His name is Kirt Kimsey and he is located in Georgia.
Anyone familiar with Darne stocks know they are very hard to do. Tougher than a sidelock or box lock. He had to remove the crazy castoff, refit a straight rod through the wrist area (standard on Darne's), convert from walnut to Koa then refit and refinish. There is so much border work of wood to metal in a Darne that it takes true talent to fit perfectly. He did it all. BTW, he is not related to me, I stumbled on him and he has now done 3 guns for me and is working on a rather nice "C" grade Syracuse...full restoration. I've never met him except over the phone. I can and will provide pictures of his work for me if requested.
Carl