How to control video height and width when using Auto Reframe?

Hey,

I'm editing a snowboard clip which had raw footage of 4:3 footage (some 2.7k 4:3, others 1440p 4:3), reframed for horizontal 1080p 16:9 to upload on Youtube.

With Auto Reframe, I'm adjusting it to 4:5. However, the tool always generates a poor resolution of
864 x 1080 instead of what I wanted which was 1080 x 1350, to upload on Instagram.

Is there any way to control for this?

Thanks