Dominic,

I have no idea. I never used them and hardly used anything similar.

Generally there is no abstract intellectual value in the targeting any specific crossover point. People out there suggest “do not cross here” or “do not cross there” but it is all BS. A channel, accompanied with it ambianic room modes, accompanied with neighboring channels, accompanied with own limitation of own performance and accompanied with the intentions that you put into this given channel will naturally recommend you where it should be crossed. Listen what that horn/driver does at the boundaries of it’s own range and listen if you neighboring channels do it better.  A generator, RTA and phase tester are usually necessary as well.