@uncle_bob: My constraints when design were to have a hot end mount in the bottom, have a 4mm hole for a PTFE liner up the middle, and have the outside dimensions at 25mm. I bolt with or threaded rod with a 4mm hole or a 2mm polished one would do the trick. I figured that would not be a hardware store find so I settled for a plastic shaft. I ran through all the bearings that would give me a reasonable sized shaft but wouldn't bust through the 25mm outside dimensions. The list was quite small.
6701
6702
6703
6800
6801
6802
6900
6901
I then went through them and saw how much they cost and how well the worked with the design.
So to answer your question, 608 bearings could be good for a 2X design if you can find magical bolts with longitudinal through holes. If you wanted to go massive and just use sheets of plywood for the hub you could even use lazy susans. If I was to build a 2X I would us the 6805s (25x37x7) that I have left over from THOR Simpson.
6701
6702
6703
6800
6801
6802
6900
6901
I then went through them and saw how much they cost and how well the worked with the design.
So to answer your question, 608 bearings could be good for a 2X design if you can find magical bolts with longitudinal through holes. If you wanted to go massive and just use sheets of plywood for the hub you could even use lazy susans. If I was to build a 2X I would us the 6805s (25x37x7) that I have left over from THOR Simpson.