Hello Collective Mind,

I just had a standing seam metal roof installed on my house.
And essentially I had a roof built over the existing roof.  That is,  I now have two attic spaces one over the other.  
My question is how can I find the locations of my vent stacks to project through the new roof?  I want to be careful not to cut the hole for my vents so that the hole would end up where there is a standing seam.  I know I can carefully measure from the edges of the roof to find the locations but that would involve a lot of running in and out of the attic to measure.  
It probably would have been easiest to just cut the holes from the outside and then route my piping to those holes.  But I sort of did it the other way.  I combined three separate vents into one and I placed a vertical pipe upwards towards the underside of the new roof.
I have a fair amount of adjustability in positioning the pipe,  but short of creating too much of a tangle of piping is there some sort of location detecter or method I could use to find the exact location of where to cut from the outside?