Aloha blinker4ever,
Good questions. You always visualize and feel the body, channels, etc. as perfectly healed. So in the SSelf Consenctration exercise you see/feel the spine becoming straighter, longer, straighter, longer, and completely straight.
The collumn of light can be as narrow as a pencil, as wide as your torso, or whatever you choose to visualize. The collumn isn't dependant on your skeletal structure - it's just a beautiful collumn of light from the bottom of your torso, to the top of your head.
Much Love,
Shawn