MIMF

The operative factor for bridge loading is the torque. If the strings are attached at the bridge then the download on the top of the saddle must be balanced by an up load at the pins or tieblock. The actual torque is determined by how high the strings are off the top (well, really how high they are above the 'center of moment' of the top, but close enough). It's easy to confirm this with measurements. If the strings were in the plane of the top there would be no torque, and the top would only need to withstand the tension/compression load in plane. A top that's at the correct thickness could do this with no bracing at all. We use braces because they add the stiffness we need to fight the torque without adding too much mass. Note that, because of 'cold creep', the torque will always win, given enough time: the guitar will swallow itself through it's own sound hole.

Ignorant question here: why not notch the saddle of guitars using a tailpiece, as resonators do, needing a lesser break angle to keep the strings in place, to decrease the download on the top , enabling a thinner, more resonant top?

Basically all tailpiece guitars do notch the saddle. Usually the string spacing of the tailpiece is narrower than the spacing at the saddle, so you need to set the string spacing at the saddle with notches. In fact I set the action height of each string by adjusting the depth of each saddle notch, then I might come back and level the top of the saddle to match the notches. I like to see 1/16" at the high E gradually increasing to 3/32" at the low E.

Brian

Duh! Thanks, Brian. I know nothing about guitars with tailpieces, except for resos. Live and learn.

Reso's are a great example of a guitar with a tailpiece. All of the elements apply, and make a difference. I have two - a modern Gold Tone Paul Beard Signature, and a 1935 Dobro Model 25. Love me some Dobro on a hot summer night on the screen porch, I play it bottle-neck due to a slight issue with having been strung up to tension and left under a bed for around 70 years...