Refacing Meshes

I'm currently trying to reflect the image of a mesh box around a cylinder to return a new mesh output. 

I have deconstructed the original mesh box to get the vertices and it's on these points that I can perform the reflection definitions. However, due to laws of reflection any points that have a positive 'Y' value are reflected along vectors in the positive Y direction and and points that have a negative 'Y' value are reflected along vectors in the negative Y direction. To achieve this the initial list of points is dispatched to form two lists. 

Once the reflection operations have been formed I am then trying to merge the lists back together and construct my new mesh using the merged points as vertices and the faces of my original mesh box as the faces. However the points do not appear to merge back in the right order and I can't work out how to maintain their relationship from the original box once they have been dispatched into two lists. 

Attached is an image of the definition with the reflection operations clustered and a file containing the full grasshopper definition. Any help would be greatly appreciated!