How should you be positioned when sewing? Like to sit and look a little down on the project or sit about so that you can see from front to the back of the machine?
I hope I am explaining myself right.

I sit where I am most comfortable, I have to be careful on the position my neck is in. I can't look down for long periods of time or put to much strain on my neck muscles. Since my cervical spine was fused years ago pain there is a constant battle.

I like to be a little high, so I use a secretary chair.
Has anyone tried lifting the back of the machine with rubber door stoppers? I do when I think of it, usually after my back is hurting.

I like to look down at a bit at my work and bought myself a drafting chair to sit on. It swivels and is on wheels (sometimes I ride a little farther than expected :) ). My problem was that my legs are short, so DH built a raised platform for my feet and pedal. The chair has a bar around the bottom for perching a foot on, too.

I have a secretary chair too. How I sit depends on what I'm sewing. I do like to have my arms and neck relaxed since I have bone spurs and arthritis in them. If I'm sewing long strips I can sit back and relax. If I'm sewing small pieces or have lots of seams to go over I have to sit closer and look more down. No matter what I'm doing, I have to get up and move around regularly.

Look at my avatar pic. It's straight from OSHA.

I didn't realize that was what was in your avatar, but it shows how we should be sitting. I just invested in a new chair.

And I learned to sit in front of the needle instead of the machine being right in the middle and having to look to the left.

The most important thing is not to hunch over, lean into the machine, or jut your head forward. That will kill your back, neck and shoulders.

I have a computer chair (actually a secretary's chair) that I stole from my desk top... it doesnt have any arms but it forces my back to be straight. I also have the "short" problem so that makes my forearms as the same height of my sewing machine.