KTL has it nailed but I would like to offer an analogy to maybe muddy the waters. I love muddy waters. If a guitar were a drum, the bridge would be most effective in the center, right? Dear god in heaven, I just described a banjo! Shame, shame. Well, guitars aren't banjos. Ignoring the neck for the moment, guitar bodies recieve most of their energy from the bridge. The vibrational length, frequency, would be the distance from the bridge to where the stiffness (MOE) transferes enough energy to overcome inertia (mass/density) in a given direction. This theory would say that regardless of stiffness and density OF the wood, as many possible different lengths from bridge to edge should be the best for all around flat freq. response. More bridge to edge lenghts of the same length should fatten that particular freq. Also means the best resonance would be had from a body made from a crosscut slab with the bridge right at the heartwood center. Now there is an ugly thought! Maybe a solid body with 1/2" thickness at the bridge tapering out to 2" at various distances away from the bridge. Not a pretty sight. If you could vary density as it approaches the edge? Like an old fashioned flywheel made offcenter? Another Kodak moment. I'm done , finally.
Plese don't take me seriously.