One of my favorite sayings is "Hind sight is always 20/20". It isn't always of course but the point here is that there is great advantage in taking a step back, after the fact, and saying "Now, what has happened here?"
This is what I did with the the Doperya brothers adventure back in the early 1900s. They wanted to make a guitar sound louder and clearer so it could compete with other louder instruments and in an effort to accomplish this they took a round spun "speaker cone", embedded it in the top of the guitar, placed the bridge in the middle of it and let the strings wiggle this cone instead of the top, thus producing a unique and louder sound.
WAIT!!!!!
What did they do? They rendered the entire TOP of the guitar non functional! They changed the nature of the sound producing (vibrating) part of the guitar radically!
BUT
They kept the same body shape. This is where the hind sight being 20/20 comes in. Does this make sense to you? It sure does not make sense to me. Having studied guitar construction methods and built musical instruments for much of the last 35 years, I have seen countless photographs of guitar tops resonating at varying frequencies showing different portions of the top going through various modes of vibrating as each note is produced. In short, in a traditional guitar, the shape of the body compliments the vibration of the top and vice versa. There is an important interaction that takes place when the strings are plucked.
If the sound producing portion of a guitar is changed from a wood top to a round piece of metal then the shape of the body surrounding the sound producing device should compliment, enhance and otherwise take advantage of the shape of the sound producing element, in my opinion.
My approach was to make the chamber beneath and surrounding the cone a continuous parabolic shape. Thus, when the sound energy radiated from the cone it would impact the back of the guitar and be reflected directly back to the cone, enhancing the resonance of the cone thereby producing a louder and clearer tone with significantly greater sustain.
In order to maximize this effect the inside of the guitar is finished as beautifully as the outside so that the sound energy has a hard glass smooth surface to reflect off of.
In short what I have accomplished is "managing the sound energy being radiated by the cone in order to minimize the energy loss sustained by the random rattling around of the sound energy in a conventional guitar body shape. I have kept close to the appearance of a traditional guitar simply because I have always loved that shape but have taken the liberty to change some things I have never liked much in a traditional "Dobro".