Rhino.Inside.Revit Curtainwall

I was able to add vertical mullions to a curtainwall by creating a new vertical mullion Revit family in grasshopper but I am not able get the mullion to alway be perpendicular to the curve. What am I doing wrong? Is it even possible? Is there another way to add vertical mullions by using an existing Revit family?

Mullion Family New Family.gh (21.4 KB) Mullion Family load from existing.gh (16.4 KB)