last time i got into a disagreement with an engineer it was over a 48'' duck below a future floor sink a RFI was generated. his answer was to physically and with great force manipulate a depression in the duck for the p trap to sit into. I cut a hole in the duck, and a SS mixing bowl despaired from the university's kitchen
I am talking about the big ass one on the stand up mixer 18'' wide and 10'' deep
set the bowl in the hole. screwed it, then pookied the edges and set a 4'' cast ptrap down in it. LOL
the next day the cook looked every where but up in the ceiling for has bowl to make biscuits