You need to use WPE, and dupe filter:
Under OFFSET colum 8 --> under SEARCH type in:
for 6 slot bag 05
for 8 slot bag 07
for 10 slot bag 09
for 12 slot bag 0B
for 16 slot bag 0F
for 20 slot bag 13
Under MODIFY type 14 then hit apply.
You need to have one of this bag equipe and when reequiping quiver put it to backpaca and then to last slot of equiped bag to make quiver dissapear.
When you make 4th quiver you need to remove bag after you make dissapear 3 quivers.
Hers how i did it...I had a quiver in f11 alredy, then i made him "disapear" and equpied an quiver in f10 and reloged(2quivers equiped now), then i put them both in backpack and then make them disaper both and equip an quiver in f9 slot and relog(3quivers), then put those 3 in backpack make them disapear, put your f8 bag in backpack and equip an quver in his place and relog and you have 4quivers.
I got 0.35 ranged attack speed on my hunter without buffs.
You can do the same to equip two same rings, or two 2handed weapons in the same time.
If you know how to use speedhack , you can solo some bosses for ex Shade of Akam in BT, it takes me 5 min to kill him with haste hunter .
Tested and works on WoWScape.