I play sitting down and my audience (restaurants) are sitting. Would I just use one extension? Doesn't that make more sense in my situation or is there some benefit to having the array up above?
It depends. In my very limited experience, if you are sitting directly
under the L1 Compact in fully extended mode you may be below the vertical coverage of the Spatial Dispersion loudspeaker, while the audience will hear you just fine. This may be a situation where a "short stack" might be appropriate. It certainly works well in this mode and I use it now for my TV audio when I'm home. (sound's great!)
You'll have to try it and let each situation determine what is best.