Color Space Issues - Filming on IPhone 9 (Rec 20 HLG)

Hi Guys, 

I recently shot some footage on my iphone 9. It shoots Rec 20HLG). When importing this into Final Cut, it asks if I want to change the timeline to Rec 20 HLG. I chose yes and it color corrects the footage. 

Now when I am bringing in white png files, they are coming in as grey. Obviously if I switch my project back to Rec 709, then the footage colors get messed up.

Does anyone know a fix for this?

I'm editing on a mac 14 inch M1 Pro 2014, running Ventura 13.5. Final Cut I'm using 10.6.8

THanks all ! 

You have to boost the levels of the PNG as they're not in Rec2020.

Thank you Yoda. You always fix my stuff within less than 10 words. Thank you !

Here's great info on how to work with HDR footage from Mark at Ripple Training.