The model take into account a gap for a "not-too-tight" tolerance. If you make a 51 mm hole you increase the gap of an additional 1 mm (i.e. the 50 mm model needs a 50 mm hole, not 51 mm). The fact that you have been able to use my 55 mm version instead of the 50 mm means that the hole you made was even bigger than 51 mm (which can happen if you accidentally rotate the drill while making the hole). However I would like that you rate the print profile instead of your user experience with the object. After all you have been able to print both models and use them.