Because of the width and height of the ribbon, you will likely experience that the sound level will fall off as you move horizontally or vertically away from the the direct listening axis, this effect will be pronounsed at high frequencies. This is also refered to as beaming, e.g. the sound dispersion acts like a flashlight.
The old and very well sounding inifity Renaisance speakers had a mid panel much like the one you have, they however operated at frequences from 500Hz to something in the range of 3kHz, i.e. like a midrange. The infinity planar was a dipole device loaded by folded transmission line.
The planar midrange was IMHO the star of the show!