I liked the RPi case by hackaholic but wanted to mount it closer to the Einsy case. I removed the excess parts from the pi case and added holes to line up with holes on the Einsy case. The back plate mounts to the Einsy case and then you can install the RPi and front plate. I suggest using some soft buffer (I used tack) between the case backs to prevent vibration noise.
Version 2 Back plate added to allow mounting to the original Einsy case. You need to enlarge the two existing tiny 1mm holes to 3 mm with a drill and the back plate will mount easily. I have marked the holes in an attached picture for clarity.
Version 1 back plate must be used with mounting holes matching this case: https://www.thingiverse.com/thing:2749883