I am currently trying to build the printer and I believe that some modifications may be required on the X-axis parts.
a) The screw hole for the X-axis idlers seems to be for an M4 screw, not M3. There is no way to insert a nut to hold it in place and the head of the M4 screw is too tall, preventing the rod from getting in. One could trim the head of the screw too but idlers with a 4mm bore are also difficult to find (at least where I am), 3 or 5 mm idlers are pretty much the standard here.
b) The 20T idlers rub against the plastic. Nothing a bit of filing can't fix though.
c) When assembled, the X-gantry seems to be a tiny bit longer than what it should be. The motor holes all line up perfectly but the assembly is just a bit too wide, pushing the Y-axis rods slightly apart. I had to take about 1.5mm out from each part of the X-Gantry for the gantries to match properly.
I hope this helps!