I also saw it in MEM even though I changed the AFCAD it says its too small which is not true...
Since KMEM (assuming you mean FSDT KMEM) comes with a GSX customization file, that one will take priority over any data in the AFCAD, so you can only set the airplane Wingspan in the GSX customization page.
And, changing the AFCAD just to edit the parking radius or the maximum wingspan, is entirely useless, because what's in the GSX customization file will always take precedence over the same data in the AFCAD.