Cached previews for 8K monitors

Hi
I use a Dell 8K monitor as may main viewing screen, along with a secondary 4K monitor for the browser, tools, etc.
I have set my preview size to the maximum (5120) in the preferences. However, I notice that C1 takes a while to render the screen everytime I make a small change. I don't see the same issue when I use the 4K monitor for the viewer.

I suspect this is because the cached preview size is too small and C1 needs to re-render every time. 

Could you please add an option for cached 8K prieviews?  I have also raised a support request through P1.  I'm using Phase One IQ260 and Phase One IQ4 150 backs.

Thanks!