Okay, here's an update and looks like we probably need to get some more advice. So anyone who wants to chime in, please do!
The holes in the bottoms of these table legs were too large for the stems of these casters. We glued in dowel rods securely, using Titebond for wood and allowed plenty of time for that to dry, which it did. We then drilled our holes to the right size.
Before the casters were installed, we were able to turn the table upright and get it placed upon two large, tall plastic drums. This way, it sat up off the floor about 6 inches. Then we could reach under there and install the casters. We wanted to do it this way, because we figured that if we put the casters on and then turned it upright, the casters might get too much weight put on one side of them, just at the moment the legs were starting to touch the floor. We thought that might bend them, so we did it the other way--by placing the table on those tall plastic drums.
Okay, here's the question now: The table is on the casters (as of Wednesday), and it is rolling when we need it to roll. However, when you take a close look at least 3 of these casters, what you see is that the sleeve nut is gaping on one side. Is there supposed to be some give in these, or are we looking at a problem here? Is this bending and going to give way eventually?
When the casters were put on, those sleeve nuts were flush with the bottom of the table legs. But, now as this table has sat here for a couple of days, it seems like there is this slight gap on one side of the sleeve nut, compared to the other side of it. Does this make sense?
Don't know if we need to go back to the drawing board here or if possibly this slight space we see in these sleeve nuts is some kind of normal variance. It gapes on the side of the sleeve nut which sits opposite where the caster itself sits upon the floor.
Are we screwed here, or are these supposed to work this way and will probably hold okay?
Thanks for letting us pick your brains on this one, guys!