loc23-
I don't run Compress, but I imagine you input the length the nozzle projects outside the vessel as L. From the formulas you are quoting, you are not using a repad. I would guess that the formula changes when L < 2.5*t or L < 2.5*tn. Otherwise you would be taking credit for nozzle length which doesn't exist. Run some examples and let us know. Maybe use t=1" and tn=.5" and run one case with L=2" and one case with L=3".
jt