Oops 3 posts in a row!?
I fail at the expertise others have in advanced forum posting.
Anyhoo...Recently (post patch) I used from 515-520 racc on Ixion and was close but not capped. I've done him many times prior with lesser racc gear (around 503) and got solidly lower racc% still although with the bow and more at 20'. (But that was with Namas so it was a bit harder to calc properly.)
My estimate is you need around 520-525 to cap if one stands just around 15-18'. I did that on gun.
That was the gist of my other post. I think using pot-au-feu is going to display a poor racc performance unless one skips stp and str in lieu of racc gear.
I'd like to see the way it could be done however I remain a skeptic.