My take on it is that it's an unnecessary expense. Not everyone will agree, and everyone is entitled to their opinion...but I think there's a TON of less intrusive, less expensive ways to get the sound you want out of your Dual Recto.
First up, what is it that you don't like about your Dual Recto that makes you want to change to MM? What difference in tone are you hoping that it will help you achieve?
If you don't like the tone you're getting, start with everything else first. Changing transformers should be a last resort IMO. Go through and assess everything else that has influence on your tone. Take a look and try different amp settings, swapping out tubes, pickups in your guitar, speakers in your cab, the cab itself, using a boost in front, running an EQ in the loop, etc. There's countless you should probably try first.
You probably bought the Recto initially because you liked the sound of some ones you've heard, whether it be in person or on albums, etc. It's very unlikely that virtually any of them had MM transformers in it, so you liked what the Recto had to offer enough out of the box to buy one.
Give it some time, try other avenues of getting the tone you want before going an expensive and intrusive route, and if you're trying to get a specific tone, let us know and we'd be happy to give advice on how to get you there.