You need the .4" DOC, or can you reprogram to run a lower DOC, Higher feed rate?
Most, if not all, of my 'max' cuts are worked out by pushing a little at a time, and seeing what the machine can do.
780 rpm? Why so slow? Stainless of the miserable variety?
You really need to be talking to a tooling supplier, as well as the machine sellers. Very likely, between the sources, someone can put you onto a far more productive solution.