I think I've decided that when my DS is in town , I'm going to ask him as my birthday present, to change the support on the table in the front (which hits my thighs if I sit up higher) and cut down the legs (wood) on the table. That why I don't have to worry about a footrest, or have my arms angled up (not at 90degrees) while sewing. At 5'6" you'd think it wouldn't be such a problem, especially with my adjustable office chair, but I can sure feel the pain of wrong posture when I'm sewing for very long!
A tip for those that find the table too high when at retreats or guild sew-ins--if the chairs are not truly folding, ladies in my guild will stack 2--this will give you extra height without being wobbley.