I don't know the machine you have but I do know they make those acrylic slide on tables that slide over the arm of your machine so you have a flat table although not a huge one. You can reach under it to change the bobbins. I am making one for myself but not having much luck so I may buy one. Something similar to this. I am not sure if the link will work.
http://www.allbrands.com/products/35...g-machine-exte
Lynda