We have recently filmed some rushes with an Alexa Mini with the settings shown in the attached document.

This has been edited in Avid and will be finished in Resolve.
We noticed that the Avid was not able to sort out the correct ratio for the anamorphic image - and we have tried a few options in FrameFlex, but none seem to get it quite right (despite following the settings from the above info).
Does someone have the correct settings for Avid MC 2018 or 2019 which will show the rushes correctly please?
Resolve handled it perfectly without any problem - so it isn't a huge issue - but it would be good to understand what settings are required in Avid.
We linked to the rushes and then transcoded at full resolution, but at neither stage could we get the correct display ratio.
The project was 1080p - which should be fine - and we were happy with a letterbox version as our final master. I assume the anamorphic element is the issue - although we did try several PARs.
Any suggestions on settings would be appreciated.
Many thanks
Jon.