I've dealt with Charles Hargett who is the Sales and Marketing Manager for Zig Kanstul. Charles has always gone above and beyond the call of duty to help me out and to add the personal attention that you wouldn't expect from such a busy company; once even giving me a factory tour when I stopped by the shop just to buy a mouthpiece.
As I understand, any horn that is sent to the shop for work gets personally inspected by Zig, but Charles is a great starting point for questions, etc. You can e-mail him at Kanstul at the following:
Charles@kanstul.com.
Good luck,
Mike