Looking for confirmation on this, and maybe a plugin:

[iBelieve]

https://sites.google.com/site/theminecraftsuperwiki/home/enchanting

http://www.reddit.com/r/Minecraft/comments/157mxr/fyi_specifics_on_armor_enchantment_damage/

I was recently told that Protection does not decrease the damage that the player takes past protection 5. I am looking for confirmation as to if this is true/ also if there is a plugin out there that would eliminate this cap.

 

[Defense]

Not entirely sure. I've seen servers sell protection 25 armor and it worked entirely, others have done the same and the armor did the same protection as protection 4. Might be a simple thing such as enabling unsafe enchants, not entirely sure though.

 

[Skionz]

Not entirely sure. I've seen servers sell protection 25 armor and it worked entirely, others have done the same and the armor did the same protection as protection 4. Might be a simple thing such as enabling unsafe enchants, not entirely sure though.

You would have to go digging in the client, or server's source. It is possible to handle this by yourself if you know the equation which I am sure is on the wiki.