I wonder if anyone can help me find the error here (see model). If I have an even number rafter spacing (rafters=6", rotated members) copy works fine if I change the rafter spacing to an odd number, copy screws up for some reason. I can’t seem to track down what the issue is.

I added a formula without directly addressing each copy, if you wish to change the centers in a few sections then can get the copy number(s) via input distance,