Ron, I think it's normal to add more HF compensation and loose a little efficiency in a wide angle horn compared to a very focused horn like the Edgarhorn. By way of the electronic crossover, I add about 10 db at 20KHz in a 12db/octave HP boost. This would mean that I am adding 4 db at 15Khz and 1 db at 12.5Khz.
In any case, I am pretty confident that you'll get them dialed in.
They image pretty darn well, but I don't think any horn images as well as a full Tractrix.