You can definitely run the MP-2 on rechargables. Rechargable and alkaline AAs are slightly different sizes and older MP-2s require a tweak to the sled for rechargables to work. Throw in a couple rechargables and see if they work. If so, you're all set. If not, you'll need to have SD tweak the battery sled.
Search the Duracell or Energizer site for capacity of alkaline AAs, I found some capacity numbers for C and D batteries a while ago, but forget exactly where.