IMHO, what you need to do is use the Radius AFCAD, or RAFCAD, design in your files.
RAFCAD assigns specific radius settings to each aircraft and parking spot.
By doing this, you can literally tailor where you want a specific aircraft to park.....and you will only need overlays at the very busiest of airports.
The RAFCAD method, along with the aircraft radius matrix can be found at
www.projectai.comThe designers of the RAFCAD method are PAI members and we are very proud of what they've been able to accomplish using Lee's great AFCAD program.
Also at PAI, you will find RAFCAD files for quite a few airports.
This process is not as hard as it sounds. Give it try, if you have a question that can't be answered here, you can post on the ProjectAI RAFCAD forum where Kevin and Matt, the designers of RAFCAD will probably answer you directly.
KJ