Advice on star alignment of wide field images please

[cosmochristo]

Hi, I am trying to get star alignment to align three images of the sky. 11mm images taken with canon 5D III, canon 8-15mm fisheye at 11mm. Each image is like the one on the left, with the "stretched" view on the right. Bias and darks have been subtracted but had no flats.
Star alignment with standard setting only exactly matches a small region.

[cosmochristo]

Sorry, scaling the image to 1/3 made the stars of the left image (unstretched exposure) disappear. Here is a full resolution crop of a section.

[cosmochristo]

A bit more information: I want to know if and what distortion settings are needed, for example. Any ways to improve the result.  Attached is a zoomed in crop from two of the registered images produced from star alignment - by placing one on top of other and holding mouse down on the top one. I want to improve on the auto registration.

Note: for this instance, not other attempts, I had exported the the images to 32bit tiff, cropped the outer circle in photoshop and increased the exposure a bit, then brought them back into PI for alignment.