My method for my two Mega Mosaics, Orion and the Galactic Centre were to make a base layer in PI with their Star Alignment, process. The GMM process which can make a mosaic from the Star Alignment base layer did not work for me. It left halos on stars, dark holes, distortions etc.
So I let the SA process register and build the base layer. Then I used the base layer from this in Registar. I would let Registar align a non linear panel to the overall base layer. Then I would build the mosaic in Photoshop, and blend them in.
This is data from 3 Takahashi FSQs (0.53m), 2 Atiks and 1 SXV ccd camera. So almost all the same set up. Pixel size is different in the SXV camera.
Very time consuming, but it allowed me to erase some overlapping regions which had bad registered stars. I do like having the full 25 pane layer in Linear Mode. I could re-blend in some panels to patch the distorted stars if necessary. However first a re run with your suggested settings.
Tom.