[Fixittt]

Well, if your having a friend do it for free, then keep it simple.
Nothing bugs someone more then being taken advantage of. So keep the design simple, so it doesnt take as long to machine.

Also simple designs are sometimes the best.

Stay with a base of about 5mm in copper a little less in aluminum. I have found that a slightly thinner base in aluminum yeilds a small return. Dont make it to thin that it could crack though.