I think if you have to sit in a chair for medical reasons..knees, back, etc then I'm all for it, go fly and have fun.....
However to sit in a chair because you believe it will help you fly better...then I say nope...for the safety reason....it's quicker to jump out of the way from an out of control aircraft when standing than sitting......
We have a few disabled pilots at our field....just last week one of them was sitting and flying when his chair was hit.....good thing it wasn't his legs