The long body shouldn't have any issues. If there's a problem,it could be that your Mega DCC isn't making contact. Try working the center contact of the carto out a little as suggested in an earlier post.
I am having problems with any of my cartos working on either my rough stack or maxi RS, this did not start until a couple of days ago, I cannot get 2ohm or dual coil cartos to work on them and I know its not the carto cause they work on my box mod,,,,,how do you "work out the center contact" why would that start doing that all of a sudden???
my LR atty still works fine on both of them
also since I first got my maxi RS the 510 connector is very slightly loose,,, has anyone else had this problem??