WRT "put my bar on the grinder"
That makes me nervous, reducing the diameter in the middle reduces stiffness in compression a lot (no effect on tension - the other direction). It may bend and allow the wheels to toe without you knowing it.

The difference in stiffness (resists bending in compression) of a solid bar vs. a heavy-walled tube is pretty small, but I suspect that a one-wheel impact (curb?) may fold a tube (buckling load) but not a bar of the same OD. I don't have real numbers but a 1" solid bar is only about 7% stiffer than a 1" tube with 1/4" wall, and a 1-1/8" tube with 1/8" wall is stiffer than both.

IIRC back in the day the original link bent under load, and the cure was a piece of angle iron welded in the center - doesn't need to be full length, my guess is a 12" piece would do the trick.