Unlike Acuity or Vision it is not possible to do a 2 Box in a single Keyer.
Ultra does have the UltraScene system where you could have 4 Boxes on Scene 1 and do another 4 Boxes on Scene 2 at the same time. However you might have to work the system a bit since you would need a CC to recall the Scene and then maybe use Aux Follows in the layers as a way to use OverDrive Aux templates to feed the sources for the Boxes.
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Les O'Reilly
Director - Switcher Product Management
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