Try different things till you find what is best for your body. There are great suggestions above.
I personally use a Gypsy Sit Upon on a chair that is normal height, but my favorite is a drafting chair (taller than the normal) as I find I my arms are reaching downward and it avoids the slouch, and consequently to pain. Take exercise and stretching breaks. If you are one of those who gets that knot in the neck, try what I call the chicken stretch -- sit straight up and stick your chin out forward (much like a chicken walking moves its head) about 10 times, then turn your head only to the right and do it again, then to the left and do it again. You look pretty weird, but that knot seems to magically go away. I'm sure your Chiropractor will laugh at you, but will probably show you how to do it. They may not call it the chicken stretch though!!!
I never sew for long as it is too hard on my back, but when at a retreat I also wear a heat belt, which seems to keep things somewhat in check.
Stretch stretch stretch when sewing or sitting.
I sure like the idea of the swoper. Have never seen one, but I think that would work well for me.
amh