One idea might be to use a secondary clamp instead of the filet knife support. It seems to me the idea would be to keep it very thin, so instead of being as wide as the original clamp, it could be very thin. However you could run the clamp the length of the blade. For extra support from swaying left and right with the sharpening method, the base could make a cross. the clamp would not have to be as sturdy as the the main clamp because the point is only to hold the knife from moving laterally. The only issue i see is finding a material strong enough to be used in very thin pieces.
After reading through this i think i should explain better. If you took the exact same blade holder that exists now and add a simple clamp to the top and have that clamp be about 1 inch long. IN addition, instead of having just a single hole for the rod to sit in, make the base a cross or X shape with the legs about an inch or more. A simple set screw at the end of each leg would hold it in place. The inch long clamp would give enough material to stiffen the blade and the cross pattern base will provide lateral support.
Clay if this sounds even remotely possible, i can possibly draw it up if you want to get serious about looking into it. I may not be translating my thoughts into words, but i think this would be an easy mod to the current design that would give ample support; assuming you can make the clamp at the top work 😉
