Thanks Fred. Good points. I note that Fusion places the parts on the bed horizontally to begin with-I am not sure how much thought goes into that. I didn't like that orientation because of the added supports which of course make rough threads. That said I am chasing the threads with a tap and die.
For now I have redone the parts with only to small holes down the middle to accommodate leads from a mounted LED. Probably that will work but I will also do a horizontal print and compare strength. With issues like this and warp I find myself heading for the lathe and mill more often than not. I guess the big print machines with exotic plastics handle these jobs well but for my one-offs probably 3D isn't always the best choice. I am still trying to see what the limits are. Still, I can make a lot good things for the lab with a lot less of my time so no complaints.

Thanks again
Fritz