Almost good, you need to find a driver and reverse its polarization to reverse what you are seeing between 1kHz and 4kHz - you need peak at around 2,2-3kHz not 1,5kHz. Deep at 12kHz could be better but I don't know how "true" your measurements are in terms of IEC711 so I'm not sure if the deep would actually occur.
OK, but GQ is specifically designed to work together it's not like KA put two random drivers together and threw it on the market. It's pretty much like AcuPass from Sonion - you can take 1700 and 2300 but it won't sound the same as 1723WT03
No, not always, but if you want to preserve peaks for ear resonances you'll probably end up with deep around 6kHz. I'm afraid moving drivers away from each other won't fix it unless the distance is really big (by big I mean >2cm) if you measure with iec711 than valleys after 10kHz is quite typical for most drivers - but not every.
Well I'm playing around with WBFK right now and it does no good with combination with Sonion 2389 which means it won't work with ED either (those drivers are practically the same). I'd say if you plan on using WBFK get different midrange. BK or EF maybe or 2600. I think working out proper crossover may not be worth the hassle for DIY unless you really have to use those drivers or you know.. have too much spare time :)
I mean I was able to get quite good response with...