I surveyed opinions on tax brackets a while back, and it seemed like there was a big psychological barrier at the 50% rate.
Most high earners would be willing to pay a 50% marginal tax rate (albeit some very grudgingly) but almost nobody was willing to go over 50%.
What’s good enough for the rich should do for the poor as well. The benefit drop off rate (effectively a marginal tax rate) should be 50% at the very most.
“For each dollar earned, I get to keep more than I give away in tax/benefits” is a cliff edge, but I think a reasonably justifiable one.