This is a fascinating project, and one that demands our respect. Someone had to do it! So please don't take this as criticism... But are we sure that shaving razors were the same as the ones used for surgery? Most of the illustrations in those drawings show instruments I don't want any barber using on me, and I think the gentleman's pained expression at having his head shaved would be most explicable, if that is a large gash or even split cranium we can see.

It occurs to me that the high-peaked spine would be most useful in creating a deep wound. While I don't know the actual shape of medieval shaving instruments, I believe there is good reason to assume they were consistent, and they weren't elaborate. The medieval philosopher Occam (or Ockam) is said to have based the principle now known as Occam's Razor on the fact that it had remained unchanged for a long time, because any way you could complicate it, you would make it do its job worse. It took five hundred more years for small-radius hollow-grinding to paper-thin steel to come along.

Occam's razor - Wikipedia, the free encyclopedia

What we know about straight razors clarifies the role of the barbers as the first surgeons. If you had to be operated on or bled, you did not want a comrade bringing out whatever he carried for casual social work.