As it turns out, vanilla (and modded) weapon scope views do not display properly in Eyefinity. Widescreengamingforums.com has little to no information regarding this issue, other than "maybe FoVegas will have full Eyfinity support." ...so here I am trying to mod up a fix for it myself.
I *think* that I have determined that the problem lies with how the .nif files used by the scope view are set up. If you go into the GECK and leave the field under "has scope" blank, you still get the zoom factor intended for that particular scope, but without the scope overlay. Doing this displays the zoom exactly like it would with a weapon without a scope, just at a higher zoom level (i.e. lower FOV value).
My theory then, is that the solution lies within making/editing a .nif file that is called on by the scope function that is formatted properly for screen resolutions such as 4320 x 900. I'm not totally sure that there isn't some other technical issue with Eyefinity that causes the scope .nif to not function properly, but this is my best estimate for how to start solving this problem.
I have opened up the vanilla .nif files for the scope view, and have absolutely NO idea where to begin. I'm reading up and going through the common nifskope tutorials that are out there, but for the most part, the scope .nifs are so different from your usual weapon/armor .nif files, that i'm not really seeing the relationships between the types of .nifs.
I'm gonna start messaging everyone who has put up scope-oriented mods, and see if their expertise can get me started in the right direction, but in the meantime, if anyone reading the forums has experience with these kinds of .nif files, or can offer any clues towards the solution, i'd love to hear it. Getting this fixed would be awesome for everyone using Eyefinity.