Hard to tell without pictures, but I would suggest floor to ceiling (or several inches above windows) and then hung so that they just touch the outside of the window. They should be full and generous looking, so 21/2-3 times the width of the window in width.

Does that answer your question?

3 times the window width for stationary panels?

Nope. You can probably get away with two sets of panels on each side of the window.

On a window that is 78 inches wide...I'm thinking 15" panels at 2.5 fullness beginning 5 inches inside the window and extending out