Wild guess, if you use the app I do to calculate how many layers of tape you need on a wedge to get an 18 degree angle on the bevel my guess it would also work with a worn down spine on a full hollow. It takes into account how wide the spine is and what size the blade is to get you into the ballpark of an 18 degree bevel which is , from what I have been able to gather, is the bevel angle spec for a brand new razor with the proper geometry.
Bob
What is this app you speak of? You certainly have my interest piqued...
"Willpower and Dedication are good words," Roland remarked, "There's a bad one, though, that means the same thing. That one is Obsession." -Roland Deschain of Gilead