Measuring port length?

[Dangrebel 89]

As many boxes as I built, my mind went blank today. I am trying to build a 30in long port with 1 bend. Do I measure in the center of the corner or along the inside port walls? Someone help a mind blank guy out?!

[ssh 924]

I believe you measure from the center.

For end correction, I think you add 0.5*portwidth to your port length.

[Dangrebel 89]

Ok the reason I ask is because if I measure from the center I don't have to put another bend in it but if I measure it from the inner port wall I have to make another bend

[StreetLegal 119]

centerline

[Dangrebel 89]

Thank yall