I have done a lot. Even with the bar stiffening mod (now obsolete with the new wide maker rail gantry upgrade) I was still having issues. So I wound up replacing the gantry and z axis with c-beam Gantry Upgrade to C-Beam.
In the process of doing the teardown for the upgrade I found that my z axis eccentric bolt holes were taking damage and wearing out of shape! It seems like the lower wheel was taking most of the load. This wear was probably a source of a lot of my wobble issues.
I think for metal you should definitely do the inventalbes gantry upgrade and consider replacing the Z axis. Either with a c-beam or a e-bay liner rail setup.
I also replaced my $5 collet adaptor with a real 1/8" collet. I think this helped too as the adaptor had terrible runout. And runout is very bad when cutting metal.
The last trick I found was to modify profile cutting. Cutting deep, single bit-width paths in metal is problematic. Any flex or runout and you hit the wall and bad things happen.
So I do a offset outline 40% bigger and cut a wider pocket first, leaving 2mm of metal. Then do the final 2 mm as a normal profile cut. This goes much smother. If I was not using tabs I could probably do the whole thing as a profile cut.