JBL generally scale their image control wave guides to suit a particular system design. Unfortunately the diy loudspeaker builder does have access to these optimal wave guides.

The implementation therefore can end up sub optimal. But as l mentioned above in the diy space it’s entirely up to the individual what they end up doing. My recommendation to to try a few options before settling on the final implement. You might be very surprised when evaluating an alternative. This particularly apply to attempting a two way system which is relatively difficult when the low and high frequency driver and horn/ wave guide are stretched in the crossover region.