I shot my longbow for about a year and a half without quiver, using POC's from about 12 gpp. I shot really accurate with them.
Then I wanted to shoot faster. So I got new arrows, which brought me to 9.4 gpp. I also installed an ultraskinny string, I went from 16 to 6 strands (with padded loops however).
In my new set-up, the bow felt a little unstable and was developing more handshock and vibration.
I ordered a Tunderhorn strap-on quiver which can hold six arrows.(wrote a review about it, see the review dept.)
For me it was just great! It reduced the handshock and made the bow much more stable. You are adding appr. 1 lbs weigth to your bow with a empty Thunderhorn quiver.
I retuned my setup with bareshafting and ended up with adding 20 grains more to the point.
Typically, a bowquiver will affect your dynamic spine with 3-5 lbs less. This is the same I noticed while bareshafting.
My arrows weigh 360 grains each and there are 6 in my quiver.
At training, I can't mention any differences with one, two, three or even all arrows out!
As a matter of fact, I was training at 45 yards yesterday. In the middle of my target there is a small yellow circle of about 4 inches. There was no difference shooting the first or the last arrow out of my quiver. All arrows were very close or in the yellow circle. But this can be my poor form....
I bareshafted with just one arrow out, being the situation you will enter the most.