BobH you are not compelled to read anything, and I do not know how you would feel if you were a working professional in any capacity for twenty years and were told how wrong you were on an objective data point about the actual production to which your profession is devoted by self taught experts in an internet forum who lack the formal training required for your profession like any, but hopefully this scenario will come for you one day. If technical writing from a mechanical engineering standpoint is too verbose, I am sorry, it does take much longer to write a short letter than a long one in a hurry.

Someone had asked how much is the concavity upon the cutting edge itself at the apothem of the arc cut in to the bevel form, while it varies from grinder to grinder and model to model I can state it is likely, today, less than .002mm. But that is not the complete story; you have ignored meaningful changes to the reduction of the edge radius and effective cutting angle. Instead of thinking about the small width of the bevel form as an expression of the razor whole, consider a common standard for today as expressed across a typical 5/8" Solingen full hollow ground blank. Between the spine and the terminus of the cutting edge on such a razor, the abrasive will extend .032mm closer to the center of the metal than with any flat object by today's meager standard for wheel forming [and with a 20cm wheel common in 1900 it will extend .644mm closer!] The abrasive must then return to that same furthest point from the spine upon the metal, and in so doing, it will encounter the cutting edge profile near to but spineward of the cutting edge terminus. This is not an area that is fixed in position, use your thumb nail and draw your blade edge toward the nail, what occurs? The blade will flex and return to position if properly ground and tempered. And thus what occurs is that the final portion of the cutting edge furthest from the spine is gently extruded away from the spine during the sharpening. Only by using a wheel (or arc chord shaped hone) can you design the curvature of the abrasive to take advantage of the unique flexibility (in the area where the cutting edge is <.2mm) of the steel used for razor production.

You may not be noticing the difference for forty years in these two examples, but that does not mean the factory razor did not have a length advantage. It did, and when it was corrected by your rehoning, your new cutting edge terminus must take place at the position at the prior concave edge's apothem, so immediately you have discarded useful metal. If you had done everything you have done for the forty years but only changing the whetstone geometry, you would have retained the length and added your higher refinement than financially possible in a professional setting today for an open razor to be produced en masse and sold in retail markets where retailers, shipping companies, brokerage houses, and steel forges must all receive a portion of revenue.