Insetting a curved face

[Anonymous]

Hi, I'm having trouble creating a face on this curved object, I'm pretty new to using fusion.

I created the original shape highlighted in blue below from the outside by creating a plane and splitting the face so it would align with the curve of the ring, however I can't do the same thing on the inside accurately. Are there any other ways to create a surface that is the highlighted part? Basically I want to cut that shape out to where the hole ends but also keep it curved with the ring. Thanks

Edit: I'm attempting to retrace my steps by starting over. How might I cut out this object once it has been aligned with the ring? The extrude/cut function will only allow me to select the shape while on it's previous tangent plane.

[TrippyLighting]

If you can export your model and attach it to the next post you'll likely get better help.

Screenshots are great to explain the problem, but for us it can be very cumbersome to explain a solution without a model.