I do not think that would be a problem with the low weight of the rotor.
I have had problems with DGBBs in larger motors, 250 kW that were mounted vertically. At least, that is what I think. But the motor manufacturer says that it should be OK to run them vertically. But, they add, do not add any more vertical load to the shaft.
I still think it is a bad idea to tilt a motor that big away from its natural working position. But your small motor should be OK.
There should not be a problem. The ball bearings can take some vertically load. With this being a vary small motor so the load does not make much of a differents on the over all bearing life. Also in this size range they only offer one bearing size and it is sized for a belting load so the bearing is much larger then what is need.
I hope that this helps
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson