Question 1: Wind direction
Wind is plane north and east. While major piping is 45 degree clockwise to the plane south. Subcontractor for stress ananlysis insist that if wind load case directing northeast and southeast respectively deso not exceed the allowable, the 45 degree wind(which is plane north and plane east) will also be OK. No oblique piping exists, i.e all lines are either paralle to southeast or north east.

Is there some theory backing up it? Basic wind speed is 150mph so I have to be very careful.

Question 2: ISO drawings
Becasue piping is not orthogonal to the plane direction, PDS model has to be rotate 45 degree to generate the ISO Drawings and make sure the N, E coordinate are true. So the iso drawing shows a lot of oblique lines which cause the drawing ugly-looking. I think it also hard for field installation.I am curious how you guys handle this situation.

Thanks for your advice.