DW, do you think that the machinery needed for this specific welting process has to be distinctly different from a GYW machine to be able to execute the stitching "underneath" the incidental flap and then out the edge of the insole?
Also, do you think that by having an incidental flap from the cutting of the inside channel, gives it some advantage by protecting / covering part of the inseaming thread? It reminds me somewhat of how outsole stitching can be protected by cutting a similar kind of channel in the bottom of the outsole.
Once again, thanks in advance for your time and efforts.
I don't know the answer to the first question...it seems to me that if it were that easy it would have been done a long time ago. A long time. Or maybe not...this method is still more time and materials intensive than contemporary GY.
As to the second question....yes Ii do think it serves as some small amount of protection. I actually would rather see the incidental "flap" preserved, than cut away as so many bespoke makers do. But that''s just my personal opinion.
That said, I cut a groove in lieu of the channel.