Jim, Certainly didn't mean to imply or suggest that I think 1/8" negative bearing is a good thing that one would want to achieve. I would certainly want to get it at least to zero. I'm not advocating negative bearing as such. However, I am having experiences with pianos that lead me to question long-accepted orthodoxies regarding soundboard construction and setup.Your comment about stressing the bridge pins is certainly a valid concern. Since I am now using the Wapin bridge configuration in every procedure I do on a piano that involves stringing (and some that don't) I realize that bridge pin stress under negative bearing is much less of a concern because of the trapping pin installed behind the front bridge pin that terminates the speaking length of the string although the real reason for the Wapin procedure is for the tonal performance boost that it give. I also see that the Phoenix bridge agraffes accomplish a similar effect which permits zero or negative bearing.
I agree that it is difficult to "experiment" because of structural limitations and costs -- plus, usually we are working on customers' pianos. I have had some opportunity to experiment with bearing on Baldwin pianos with the vertical hitch pins. (One particular SD-10 as well as some smaller models). In those instances I found best results from reducing rather than increasing bearing -- although I never went into negative territory in those cases.I think this is an exciting time in the development of the piano and I believe much of the advancement in knowledge and technique is from rebuilders such as yourself who have the vision (and guts) to go beyond just copying what was there.