I'm about 5'7" or 5'8" and I love FMQ! I would much rather quilt than piece and have often resorted to buying tops on eBay so that I've got something to quilt.
I used to forget to breathe - I'd get hot and sweaty and my shoulders would just burn while I was fighting that quilt. It took quite a while to get over that, but now I really love quilting.
First, I set up my machine and the quilt so that the weight and bulk of the quilt weren't fighting me - no more big "logs" of quilt dragging and pulling toward the floor.
I have my sewing machine cabinet backed up to a large table and I have a folding table tucked under the wing of the cabinet on the left side so that the weight of the quilt is supported all around. The whole quilt is piled up loosely on the tables and under the arm of the machine, and pulled smooth and flat in the area around the needle.
When you're in the middle of a king-size or queen-size quilt, this is hard work, so fortunately it doesn't last long. I start in the middle and work outward so that I get the hardest part done first and so that any "ease" in the fabric has a chance to get quilted out before I get to the outside edges.
Then I found that you can also apply the borders and quilt them *after* you've already quilted the main center part of the quilt - not having borders eliminates some of the bulk that has to be pushed through the arm. Every little bit helps when you're quilting in the middle of a large quilt.
I don't get that tension in the shoulders and neck that I used to get - I think that disappeared about the time that I slowed the machine down and quit trying to sew at jackrabbit speed. The tension was coming from feeling out of control and not knowing where I was going, next.
Now, I practice on a Dry Erase board over and over - when I can "autopilot" through a design and cover the board with it without thinking about what to do next, I'm ready to sew the design.
That alone took a huge amount of stress out of FMQ.
Feeling as if the design is going to flow out of the needle without my having to think about it was a huge turning point in really starting to enjoy the process. :)