I just purchased a reconditioned 5D and I can't wait to use my Leica 19 2.8 on it. I've read the pros and cons about mirror filing vs. filing the lens's rear flange. I think I'd rather keep my Leica untouched and go with a mirror filing, but I don't feel qualified to do it. Is there anyone out there who can take this on? I'm happy to pay whatever.