Who would you recommend to make custom clothing? I'm considering having a hood & thumb loops added to a Patagonia Capeline zip-t.

Except that I'd probably want to try it myself, I'd hire my neighbor who is an absolute magician with a sewing machine. You might want to call on a couple small high end clothing stores and ask who they recommend as a seamstress.

well the 2 garments I have owned with thumbholes, have a sort of "U" shape that is squeezed at the open part, where it meets the cuff. The problem with that is they use a very small trim, and I don't know where you get that from, but I know a guy who is a crew coach, and when they are out on the water in the morning, they use sweaters with like a buttonhole stitching, if that is agreeable to your hands, then thats probably the best bet.