Does a wide initial gap in a Karlson lose loading?

[freddi]

if the coupler in question uses a large initial wings gap - does it at some point lose loading small-signal and otherwise? It its vented towards the top then Fb can shift upwards a couple of Hz which might be difficult to see-saw by tuning a relatively small rear chamber.

I liked the tone of this coupler and 18" (or 15) with 1.2" gap a lot and not much at all with same wings swiveled in to provide a 5/8" gap. There wasn't a lot of difference in aperture area. Baffle angle was 23 degrees and port board canted forwards 10 degrees

I had a notion that with outdoors ~ground plane plots that a tighter gap at the top could force more LF to the ground thus altering that perspective a tiny bit.

http://img483.imageshack.us/img483/9605/gp12421lx7.jpg