Jazz Man,
I went with inverted on my DIY table, and my thrust ball is just below the top surface of the platter, which is 3.5" high and weighs 29 lbs. . I posted a sketch in my thread "Intro from newbie tt builder". I don't know how scientific my initial thought process was, but I thought about the difference between hanging from an object I was gripping with my hands, and standing (balancing) on a small object. The former is more stable.
I ended up with .001" diametrical clearance between the axial bearings (2) and the shaft, and am using a mediun weight oil. I'm just going to let the oil run through, and I have a plugged hole at the top where I will add more as I need to. I can even use a dip stick to check the oil level at the top. I have been playing records for about 30 hours now, and I get very little oil running out the bottom. I listen with a mechanics stethoscope for bearing noise, and hear nothing.