I was worrying about all that before I tried it loosely together, but having had a good look it will work I think, it's the string holes in the block that need to be just below the slots in the nut, or where the strings break over I should say, I'll prob have to do a bit of filing to the nut slots to get it to be happy. I've tried poking the strings thru just loose to ensure that there is sufficient "path way" and it looks like a goer..
As mentioned I've got a zero fret thing stashed in my junk which I could call into play if the regular nut doesn't want to co-operate, I can bully that in place if I need to 😁