Printable Mendel Y axis

I've been slowly tweaking dissidence's printable Mendel frame, and I think I'm not far from something useable. I started thinking about what's next, and thought a rail and wheel might work for the Y axis, so I made this! Its supposed to be an upsidedown T rail with tab&slot to chain the pieces to make longer rails, and three wheel pieces that go together to sit firmly on the rail.

Yeah, its not so pretty. When you print 3 small wheels like this, the stringing between them is so bad that when you trim them, they become square. The smallest doesn't even have a hole thru the middle.

The rail looks OK, but the tab&slot doesn't work. I'm going to try making it wider. Also, for this to work well, your printer will need to be better calibrated than mine. The rail has a bit too much plastic extruded at the ends, which would make the wheels, if they worked, tend to stick at the interfaces. Another thing to do is print the part on a diagonal to get the most length possible out of the plat