Sharepoint 2010 - Folder Permissions

I have a document library which has the hierarchy as follows:

Root
  |---- Folder 1
  |         |----- Sub-folder 1
  |         |----- Document 1
  |
  |---- Folder 2
            |----- Sub-folder 2

My requirement is to have users to:

(1) Create and delete stuffs at the sub-folders level but not at the Folder level,

(2) Not have the ability to delete Folders 1 and 2.

I have tried customizing permission levels but I can't get the desired result for (2). Is it possible to do so? Any recommendations or workarounds are appreciated. Thanks in advance.