I posted this earlier but got it in the wrong category. I always struggle to come up with unique and attractive sound holes. I starting to wonder if we need them.
I recently finished a 3string build with a piezo pick up and because the box was small, I opted for no sound hole. What I found was this guitar would handle a lot of volume and a lot of gain with very little feedback issues. When played unplugged while not very loud did no sound much different from my other builds that have sound holes.
So my way of thinking, if a CBG has an electronic pickup then it is intended to be played that way and a sound hole is unnecessary. If I were to build an acoustic guitar, I would put the sound hole in the back or top. My reasoning is this, the sound comes from the top and the sound hole's sole function it to allow airflow in and out of the body cavity, thus allowing the top to vibrate more freely. So, the more material left in the top would mean more vibrations. It would certainly make builds easier, by giving more top surface to install volume and tone knobs, switches etc. It would make a better-looking build in my opinion. I would like to hear other people's thoughts on this.
With any topic like this, you're going to get a whole lot of "traditional luthier" insights on why sound holes exist and what they do. However, traditional luthiers probably wouldn't make an instrument with a cigar box and a stick, so - while those fundamentals still apply - take them with a grain of salt.
I'm more of a fan of people actually trying things and reporting their findings which is exactly what you did. A+++ to Ron. You tried something new and had success with it. I think you're actually teaching all of us something instead of the other way around.
For what it's worth, I've seen several builders that make electric gits without sound holes. As you state, the hole may actually increase feedback and serves little purpose (other than aesthetics) on a git that will likely never get played acoustically. I've also seen builders fill the entire box cavity with wood (effectively making the instrument into a solid body guitar with a cigar box wrapped around it).
I am sure there are many thoughts on this. To my way of thinking the sound comes from the top, is basically the surface of a speaker albeit a very flat one. The purpose of the sound hole is to allow vibrations. If the body cavity were a vacuum, it would not vibrate. It allows the guitar to "breathe' vibrations actually turn the body cavity into a bellows.