What you are trying to do? Some real life panorama on 8 monitors or in game panorama?
If that is in game it is singleplayer or multiplayer? Is view trough panorama interactive (ie. can one player influence what another can see on panorama display?).
Can this whole panorama be seen at once by one player?
Your approach while easy on game designer side is very resource wasteful.
Instead you should do trigonometry:
Flatten your problem to circle and single camera represented by triangle.
Now calculate what portion of circle that triangle camera can see. Add like 5% margins on sides.
Render only that (ie. place single 2d camera in word and render to texture.
Then pan that panorama circle to face correct direction.
Math for it is very simple for situation when player is always in center of panorama, gets a bit nasty if player can move.
But it is just elementary school trigonometry.
PS. I would start testing with making panorama camera fov 5% bigger, matching it rotation directly to player camera rotation, then rotating panorama circle to same direction.
This should work fine if player is in middle of panorama.