I had some excellent experience on jury duty, sitting in a chair. Two things are important to me, sitting in a chair: sit on the edge of the chair, as I believe you describe (a chair with four legs solid on the floor); then, one foot flat on the floor with the knee at about a 90 degree angle, and the ball of the other foot resting on the floor under your tailbone, approximately. I sit this way all day at the computer, and have done so for the last twenty years.
I thought my experience would translate into progress at the lotus, but after a lot of years, I decided I would have to figure it out, instead.
The Tai-Chi teacher Cheng Man-Ching mentioned an ancient Chinese description of meditation in one of his books: straighten the clothes and sit precariously.