I don't like it when the small tow truck spawns when I'm in a 747. It feels odd. I'd like to have only the bigger trucks with this plane, but didn't find anything about in in the manual. It seems it's a random choice every time.
The Pushback truck is not obviously chosen at random. It's chosen based on your airplane total weight so, the smaller truck will only appear if your airplane total weight is less than 175.000 lbs, which is precisely the maximum weight that small truck can push in real-world. Since a 747 empty weight is at least 330.000 lbs, it's not normally possible to see the small truck with such a large airplane.
However, there's a secondary parameter that drives the choice.
If your airplane parking radius (as specified in the scenery AFCAD) is smaller than 18 meters, the small Truck can be selected, even with larger planes, because GSX correctly assume the larger truck won't be able to maneuver in such a small parking. A 747 won't obviously fit there, so it shouldn't happen.
BUT, if your scenery has a parking that was supposed to fit a 747, but with the radius in the AFCAD wrongly set to be that small, you MIGHT see the Small truck, even on a 747.
Of course, you can override the Parking Radius in GSX. In this case, it won't be enough to set the "Max. Wingspan" value, which is only used to allow GSX to let you parking there, but you must change the Radius too, which drives the choice of the Pushback truck as well.
