Reckon you have lots of choices, listen to everything you can.
My perception would be that the elliptical horns Simon is suggesting if going straight, would be a better bet than mine because you will be able to get them tighter together vertically. Reckon that may help with integration as you’ll be near field. If snail, I think you can hang other drivers/horns in the mouth and use a digital xo to time align. Bass could be horn or open baffle…