Matty, I can understand your concern about a bow quiver can change how your bow feels in hand, and especially how it affects how the bow shoots. I had the same experience years ago and thought that I'd never try a bow quiver again.
Then we started making the (Eagle's Flight Archery) "Mini" series. They weighed about 3.2 ounces and you absolutely could not tell they were on the bow. Since then we have added several standard 4 arrow models and even 2 jumbo 4 arrow models. Most of these weigh under 5 ounces and still don't change how the bow shoots.
Recently I retested our EFA quiver versus one of our competitors quiver. I also had a friend of mine to participate as well. (He is a very qualified archer who owned a successful business manufacturing components for compound bows.)He shot a Horne longbow whereas I shot a very lightweight horsebow made by Lucas at Saluki. We shot three arrows each at a one inch bullseye at about 12 yards distance.
With a bare bow the 3 arrows for each of us was about a 1" group right in the bullseye. With the EFA 4 arrow "Navajo" quivers on the bows, (weighing about 4.4 ounces" the results were the same with no change in how they shot. Then, with a competitor quiver (weighing about 9 ounce, but touted as a lightweight) the same 3 arrows were shot again. This time they impacted 2 - 1/2 inches to the left of the bullseye, again consistent with both bows. At 15-16 yards that distance grew to about 3 -4 inches. I believe that it would be safe to say that at 20 yards you would be off about 4 -5 inches.
You can get used to your bow not shooting where you point it, but there are a lot of us who don't want to go there. That's who we sell to.
Rob, it looks like your getting good use of those quivers. Don't you like Tim Roberts work? He's a great guy to work with.