X,
The quiver I have is 32" long on the outside. Rod makes different hood lengths depending upon your arrow length, so 30.5" will be no problem. My arrows with Grizzlys on them have no problem and they were around 33" in length, overall. I got the longer hood. Pic of the nock end with eight arrows in it with room for more.
I have had no problems with fletchings - easy in and out. Quiet, too if you are not ramming them.
Inside diameter of the point end of the quiver is 3.75". Here is a photo of the same eight arrows with field points on them and there is a ton of room. I did not push the points into the foam for the photo. I have roamed around the hills with field pointed shafts laying like this and if you don't go head over heels the quiver holds them in just fine.
I carried 6 arrows with broadheads (they were in the foam) during last years hunting season with room to spare. The ends of the quiver are fairly rigid, especially the point end. The nock end is slightly flexible but only when squeezed. The part that lays across your back is flexible to be comfortable and to keep your arrows quiet. I traveled through sage brush, pines and other trees with very little noise if I was doing my part.
I am not sure what you mean about "a good gravel carrier". I would think that the pocket (only one) will not deform the quiver no matter what you put in it but too much weight might be bad for the fabric. I don't know what you intend to carry in it but mine carried my hunting license, stringer, spare glove, GPS and a few other small items and I still had room left over. I hope that helps. If you have any other questions, I am sure that myself or others can assist. The other option would be to give Rod a call - he is very helpful.