Hi Roger,

I picked the various construction lines from your original model.

After making the revolve I extruded a circle (I created the circle from the orientation of the lip, size from the cutout) to intercept/trim the main body.



I then copied the edge of the cutout, trimmed that new curve and made blend to lines I had created from the top of the original cutout.




I then extruded the blend curves (+ a line connecting them) and trimmed the top of the cutout.




I then selected the edges of the cutout and merged them.


- Steve