I don't drive a 210 (yet), but a member at my club does. He uses
MM4 on clay!
He has worked on a decent base setup for a while, but he's got the mid running sweet for both dirt and astro. He had two cars, one RM, one MM. He stopped trying to get the RM to run well as he was having problems to get it balanced and found himself only driving the MM4.
And if it means anything to you, he's one of the quickest guys around the track
So what I'm saying is, perhaps you could try out the mid motor on dirt?