The metal arrow gripper channel is held in place by an allen screw. If you use some warm soapy water,you can slide the rubber gripper out of the channel and remove the allen screw. I believe there is a second hole in the channel,but it is not quite in the middle of the channel,and I believe it is smaller. You may have to drill it out more.
I have used Selway quivers for years and have always been happy with them. I have just used them the way they were,and never really paid much attention to where the arrows were.(but that is just me,if it aint broke,I don't mess with it)