I think you are making the mistake when you publish to cubic and then modify in Capture NX.
I really suggest you install Smartblend and export in Spherical format, edit in Capture NX and then import back to Panoweaver and publish. If you really want cubic do that after colour correction.
I assume you are exporting to cubic to touch up the Zenith star and Nadir tripod patching? If so, that is fine but do not do colour correction or sharpening in cubic mode only the patching. If you use .tif format from Cubic to Spherical and back to Cubic again etc you will not lose much (in quality) as .tif it is a non lossy format.
My workflow is more like this:
- Raw images processed with Adobe Camera RAW (ACR) to correct Vignetting & Chromatic Aberration something Panoweaver cannot do. Export to .tif image format.
- Import .tif images into Panoweaver 5
- Set size to output to something I know is around the "real" maximum of the stitched image Custom usually but 6000x3000 (Canon 5D and Sigma 8mm) or 10000x5000 (Canon 5D and Canon 15mm) is close enough.
- Stitch to Cubic, export in .tif format and patch Nadir and Zenith as needed in Photoshop and save.
- Import .tif back to Panoweaver 5 and convert to Spherical projection.
- Export .tif image and do final colour adjustments and any other needed corrections including sharpening in Photoshop save as .tif.
- Import final corrected .tif and sharpened image and publish.
Hope this helps.