Kossel Mini Carriage with integrated straight belt slots

Can someone who has printed this please confirm that the belt slot size was correct for them. I made it fit for my printer, but I'd like confirmation that the slots print well on other printers too. The belt should slide in reasonably easily but then be secure once inserted.

Designed for GT2 belt, 6mm wide, 2mm pitch. https://www.adafruit.com/product/1184

Remixed from http://www.thingiverse.com/thing:221667

I wanted to add strength by increasing the thickness of the belt holding par