In the RDNA forums (somewhere) there is a really nice discussion of IBL and someone (Traveller?) posted a shader setup and set of masks he uses. Basically, you create an IBL sphere which has left, right, front, back, upper, and lower areas. You can vary the color and intensity of all these areas through the inputs to the nodes. You can use it then to give a directionality, and even color to the IBL, which can give you some really nice effects.