Entry for August 2019's Guitar Of The Month is now open!
I've seen some guitars where they used ferrules in the back and in the front. Just to prevent to damage the wood. I don't know if there is a standard distence to lower a tunomatic bridge. I just bought one and took the dimensions of the bridge. Check how high the bridge is. After that, compare this with the height of the nut. If you make a little drawing of this, you should be able to see the distance between the strings and the frets. Because you can adjust the height of the bridge, I lowered the bridge so the strings touched my last fret. This leaves me enough adjustment space to get the bridge on the exact height. The tunomatic bridge has a fixed radius. So i'm thinking of using the same radius for my fingerboard ( a radius of 350 in my case, but I don't know if this is a standard). Hope this helps a little bit.
don't know if you need a certain distance. I think best way is to make a drawing and pay attention that the strings just hit the saddle of the bridge and nothing else. I'm making a body through with a tun-o-matic bridge. I'm going to sink the bridge because i'm using no angle on my guitar neck. I made the necessary calcultions, and i think it can be done. Hope to post some pics soon. (already made my templates etc... starting the real work any day now)