Ken, thanks for the thoughtful post. The thing that has so far kept me from using tonerite is the fear of doing harm. Somewhere I read of one or two bad experiences, guitars that sounded worse, boomy bass and muddled mids. For certain this appears to be a small minority of the reported results, which generally range from very positive to small change. Suburude, have you tried your tonerite on either your Kopp or D-18A? I'm be interested to hear your description of the changes, if any.