Acoustic Guitar Construction

In the pic I attach - it's from the web - I need to purchase some cf rods/tubes.

Do you know what range of diameters are normally used for the rods? Would tubes be as stiff?

With all due respect -- in my opinion this is a cure looking for a problem. If the sound-board is not properly humidified those rods will do nothing to stop the a concave top belly and the subsequent pitching of the neck and its set angle. $.02

Hmmm...well, what I want to try is a cantilver neck, and these rods supposedly will allow me not to use an utb.

But I need some education, and really value your opinion:
1.My understanding is that the rods will relieve the string pressure off the top. Is that correct?
2. In looking over Rick Turner's latest (that pic is not his) that he is careful that the side blocks only touch the back and sides - in other words there is a gap between the side blocks and the kerfing. That makes sense to me.
3. In the past you've said that you like the idea of a cantilevered neck, are you still of that opinion?
4. If there is no utb, some builders are running the x-braces way up into the upper bout.

Of course this all is dependent on the idea that a 'freed' upper bout will allow that bout to add whatever it has to the over-all sound, rather than effectively damping it above the utb.

I think I may have said I like the cantilevered neck design on the McPherson? Its only my opinion but this idea has been floating around for 25 years -- and I believe your guy Rick Turner is the one that published an adjustable version as well -- so after 25 years is anybody using it? But I don't think it will hurt anything. Oh yeah --- the string tension "easily" setting the sound board in motion is what produces the resonance. Just imagine the path of the tension, nut to saddle/bridge, (first!) then along the sound board to the sound hole, (if there is one) to the neck block. Then, this arrangement (if I have it right) does not apply resistance until after the sound board is stressed.

In other words the string tension causes the bridge to roll forward stressing the sound-board (which is why the X intersection is closer to the bridge on modern guitars) -- how can those CF rods affect that?

I am not sure this arrangement would prevent the neck from rotating around truss rod by bowing the back. I might be ok but it is such that I would want to do a real structural analysis to say.

On classical guitar a few luthiers including Jeffrey Elliot open up the UTB to free the upper bout.
http://www.elliottguitars.com/. It is a lot easier to understand how the design will react under load. I just want to see the load transferred to the rims. I am not sure I am seeing it in this design

I don't think the intent of the rods is to affect the bridge roll at all - if anything, eliminating the damping in the upper bout should allow the extended x braces to get excited well into the upper bout.
The rods are to protect the soundhole and free up the upper bout. As a 'side' benefit, they stiffen the sides as well.

The cantilevered neck also take pressure off the ub, and can raise that angle at which the bridge is rocked.

Snake oil? I hope not, I like the little fantasy picture I've painted in my mind. LOL.

The picture was Howard Klepper's, Rick Turner uses 4 rods. Kent Chasson, rods and cantilever. (pic below).
Dave Faoite (below).

I've got to think these guys have already done the testing that John would want to do? Unless it is all a marketing ploy? Could be, I suppose.

i value your feedback, it may stop me from wasting time on needless procedures, though the cantilever neck is something I'm pretty sold on.