[Funky61]

Yes, the lugs are carrying the load. I took a look at my stock steel wheels on there now and the hub does not seem to be supporting them either. I checked fronts and backs and there is a gap where you'd think the hub would support; but it does not seem to be resting on anything. Maybe support is on the inside that I'm not able to see.

I first bought special lug nuts to bolt these wheels on. They were Standard thread but had the outside threaded as well, so I could mount the center caps. As you mentioned the center hub was too small, so I had two wheels opened up for the front. The rears were OK I believe, but again the offset was not right.

I went with spacers on the rear first and just mounted the fronts with my new special ordered lug nuts. With stock drums the front wheels rubbed on the inside; either the control arm or caster arm not sure. Chewed up the stick-on balancing weights. Using the spacer eliminated the rubbing issue.
I have/had driven it for over 450 miles around town using those spacers, without issue, and she drove very smoothly with those radials (235x70x16) all around.

*The challenge becomes when you want to change a rear tire. When my Burb was lower, it required two jacks and/or supports. I'd first lift to get it off the ground; position jack stands, then move jack to the rear bumper area and lift to take body weight up off the suspension just enough to work out the rear tire.
This would not have been an issue with the stock suspension as my suburban sat pretty high, and only applies to the rear. I had a 4 or 5" drop in the rear.

Currently I run the stock steel skinnies with 1 1/2" block drop and stock rear coil springs and front torsion bars turned down slightly.