I think that their Regenerationn should be at least Mid-level, since the Eds at least have shown that they can survive getting totally flattened a few times. Some examples I can think of off the top of my head are in "Don't Rain on My Ed" (Ed and Eddy getting flattened by a steamroller), Big Picture Show (Edd getting flattened against a wall by Ed), and "Floss Your Ed" (Edd getting flattened against another wall, again by Ed).