Since the 737 wings are not "high" enough for GSX' animated fueltrucks, we "trick" GSX and move the fuel point further out to the wing, so it's higher. This way all animate fuel trucks (with the people moving the hoses etc.) work, also via the ground/hydrant refueling.
How to? Open the "customize airplane" menu in the GSX menu, click on "fuel" and enter the following measures: 14.36 -6.56 3.57. Click on "save".
(Keep in mind this will create a custom aircraft profile)
Tested with the 700 and 800.