The perpendicular ribbon array would give you a fairly narrow on-axis swath of vertical dispersion, and probably an on-axis hot spot where the two patterns intersect. The combined patterns would look like a plus sign.
You might instead mount one ribbon above the other, with the upper ribbon angled back about 10-15 degrees (probably need an angled-back upper section of the front baffle). The ribbons don't quite beam like a laser in the vertical plane; more like a flashlight, and a roughly 10-15 degree splaying ought to give good vertical coverage for standing listeners (assuming seated listeners to be roughly on-axis of the lower ribbon).