that looks like an easy mod to make!
design a braket that takes the mounting points from the EK9 hub and the mounting points of the rx caliper, design the braket to hold the caliper sightly offset - ie that its rotated from the horizontal plane upwards, make the braket threaded then the bolts going directly through the caliper will go into the braket and the addtional holes will hold the braket to the hub.
Easily said i know but i've done something like this to be able to but different calipers on my race car with a custom made braket to fit them onto the car.
keep us posted on how you get on.