Yeah, Steve said it worked a lot better full range with 2 different drivers in each cab.  
His experiments are in the Hell, those aren't big ! thread.  

For full range, one crossed low, used as a sub, and one used higher, something like a scorpion.  

Some have reported problems with the seperate tweeter/horn on top -- too much distance between sources, until you get back at least 35 feet or so.  Good for outdoors or Auditoriums, Bars, etc., but sounds don't blend well up close.  

Coaxial sounds like a good idea.  
It worked for Jensen...