I am vaping a Merlin as I type this. I normally run the air wide open for DL hits but just tried turning it down almost fully closed and it does give a decent MTL hit. I don't have the best build in it for MTL @ 0.4ohm/40w but I bet it would give a good MTL vape with a higher ohm and lower wattage build.
Edit: Forgot I was using a Merlin, not Serpent.
oops, my bad. edited original. I am vaping a Merlin not a Serpent. S shaped logo threw me off. I really should break out one of my Serpent Minis.