I've added some new things to JSBSim. The first is a new FDM configuration item called pitot-angle that goes in the metrics section. This will make a slight change in indicated airspeed, as the speed is now calculated using a pitot coordinate frame rather than the body frame. In most airplanes the pitot frame will be rotated nose-low by a few degrees from the body frame. About -4 degrees is a good estimate.
The second change is the air refueling onload rate is now configurable. It used to be a hard-coded 6000 lbs/min, which is OK for cargo/bomber type aircraft but too much for fighter types, which onload in the 1000-2000 lbs/min range.