I think what you are looking for for the armrest area, is a need to set a cplane to get the working plane at the angle you need to work with..

So you can draw a line that is perp to that crossing line for the armrest, then use it to set a cplane to that view (You can do it with a construction line while setting the cplane, but this is for illustration)

Then the front view will look staight down that angle, so you can adjust the curvature as needed:





I had a couple guys from another software asking me about guitar work, and I told them I would make a video to address a couple areas.. It will be much easier in MoI, but Maybe this weekend I will get those videos together and respond to them, and you also here... I got overwhelmed with a tournement, then my daughter broke her elbow, but it's settling down a bit now, so I'll see if I can spit something out that can help here a bit..