How to I rebuild/align a UV grid for priorly misaligned, merged surfaces?

Image appended above is before MergeSrf,

Image appended above is after MergeSrf.

Is there any way to align the UVs? I tried Rebuild but it still followed the profile of the priorly unmerged surfaces. I would prefer if the UVs of the spherical section followed the UVs of the more elongated surface.

Uploaded Rhino file:
rhino_tandikan_plumevar2_forum.3dm (628.8 KB)

Thank you!

Why are you trying to merge that? Its not a case where it makes any sense, you’ve just created bad geometry with the placement of that singularity. Merging surfaces is something one does not actually normally do.