getting super resolution of a 19 000 x 9500 px wide file

I read that size limit for Super resolution is 65 000 pixels 
I'm able to get super resolution on smaller files - and I like results for those smaller files. 
But no go for those  larger ( Tiff ) getting this dialog - 

Also - the preview is not working - looks extremely pixelated- as in the screenshot. 
OSX 10.14   64Gb RAM 

Radeon Pro 580 8 GB