Gina and Mechano're right - it'll work with the America master cylinder but to get the benefit of the twin disks you need the right master. With the standard master the pressure supplied by the master is divided across two callipers, lowering the pressure on each set of pads. The piston in the speedy master has a 2mm longer throw which gives you greater hydraulic pressure at the callipers.
If you're only going to twin disks for appearance it probably won't make much difference until that day that you really need to throw the anchors on. I'm upgrading because I need more braking when I tow a trailer so I wouldn't even think of compromising my braking by using the smaller master.
