I went to a dual res MC when I switched to front discs so the MC is designed for Disc/Drum. You can see the MC in the conversion from my post on Disc Brake Conversion from a little over 2 months ago. It is fairly small so it worked well without much clearancing. It might work with drum/drum if you set up a proportioning valve for that purpose, I’m not really sure. I think most everyone is running the stock single res MC if they keep drum brakes but I also like the idea of a dual MC-maybe someone has done it out there.