Split bowls really serve no purpose. If you think about it, couldnt you just fill your bowl with half of one flavor and half of the other flavor? These bowls are basically just gimmicks and are soon forgotten by the people who know they aren't worth it. On top of this...mixing your shisha will get you better results instead of separating 2 different flavors.
With that said however, I have set a bowl up, with 3 different flavors. I called it the "Citrus" blend and I still do it to this day because it was so nice. Get a large bowl, and put Al Amir Orange, Al Fakher Lemon, and Afzal Lemon-Lime. You wont believe it...again, not mixed. Try it sometime