After having played a little with corexy on a small smartrapcore I decided to design a corexy to fit inside an Ultimaker box with a print volume as close to the original Ultimaker as possible.
I had a ultimaker clone box in my junk-box :-)
Here it is before mounting below the top-plate:
The bearings are 624zz nearly same size as the pulleys. XY-motors are nema-11.
To overcome the smaller width (5mm) of the bearing split the GT2-belt in half (simply with a pair of scissors)
The printing area is 195*220*200mm^3 In my opinion close enough.
Have fun
niels