Leaving aside the question of whether bridgepin material has a significant effect on tone, I would be correct, would I not, in assuming that the main function of the bridgepin is to ensure that the ball-end of the string has maximum contact with the bridge plate. Hence, unslotted pins (which require slotted holes ) are preferred to slotted pins.
It does seem to me however, that many owners might prefer their bridgepin holes to be perfectly round, with no visible slot, so what I wondered was whether there would be any drawback to using the Stewmac Bridgepin slotting Tool to create a partial slot in the pin, about 1/4" long just under the bridgepin collar, and then, using one of their specialist saws and/or files, filing a partial slot for the string in the bridge, which would enable the full width of the ball end to sit against the bridgeplate, but which would not be visible at the top of the hole.
An alternate procedure, which would, I think, work, would be to file a flat on the bridgepin just underneath the collar, to accommodate the string thickness, but aesthetically, I think grooving the pin with the Stewmac tool would be preferable.
Obviously, both slots would need to be long enough to ensure that there would be no "kink" in the string when tensioned up, but I think it would be perfectly do-able.
Seems to me that this would give you the best of both worlds, but from previous experience of having bright ideas I am sure that either A: it's already been thought of , successfully implemented, and several builders have been doing it this way for a long time, or B: there is some compelling reason why it hasn't been implemented before.
