A recent addition to my darkroom - found doing a Google search on Fotoman cameras - I have no connection to Fotoman other than being a customer.
Fotoman made ( and I think a few are still available ) a rather neat film slitter for cutting one 8x10 sheet into two 4x10 sheets. It also has a notching punch to add a notch to the film half without one. I have sliced up a few sheets and it works very neatly - you insert the film into the machine - lower the bar - slide the handle - push the punch - and you are done. I had been cutting film using a regular paper cutter and I must say the this makes it a much easier job. It is a little on the expensive side ($150) but I believe it will eliminate the waste from mistakes and open up a lot of film choices other than the annual Ilford 4x10 special order.
It is mostly made from aluminum, so I would expect it to last - It takes a regular mat cutting blade like a Logan.