Tom..and others,
Blade length has nothing to do with "most" of the centers. For instance, On a Model #25-5" or a Model #25-6", or a Model #27-5 3/4" the dimensions are the same. The "center" block requires a handle measuring: 1 1/8" X 1 1/4" X 3". The smaller Model #26-4", "Pathfinder" requires a smaller piece measuring: 1" X 1" X 2 3/4". The big block required for the Model #12-9", or #12-9", #14 grind is: 1 1/4" X 1 3/8" X 3 1/2". Even though the #12 and #25 both are forged from 1/4" stock, the remaining tang steel left to install the handles are of different dimensions, thus requiring differents block sizes. These are all the most current and up-to-date specifications from the Randall shop. Hope this helps..Best, Capt. Chris