Parametric Bridge Grasshopper - Help!

Hi Everyone,
I am currently working on a Bridge in Rhino & Grasshopper.
The Bridge I am trying to make has 2 pylons in left end and only 1 in the right end. I have made a script, but my problem is, that I can’t figure out how I can gather the 2 point (marked with yellow) in to one point which should be at zero on the breb.

Hope that someone has the time to help.
Best regards

HT (7.0 KB)
HT Bridge.3dm (8.6 MB)

Is this what you are after?..

HT (15.2 KB)