Unfortunately, I didn't take photos, but you're about right.
Might need to go a bit higher so the wheel-opening shape has a very gradual transition as opposed to an angle.
Laying it out with some 1/4" masking tape on the outer quarter panel before you cut really helps visualize.
I cut the flange area first: a vertical cut at the contour where it folds inward.
Leave the flange attached to the quarter at the top.
Then the inner, checking the flange fit and opening shape as you go.
The nicer you cut it at the flange, the easier it'll be to refinish by back-masking and spot-blending.
You'll be better off - not burning paint - with panel adhesive than welding.