At approximately 200 knots (~100 M/s) the wings will sweep backwards, below that speed the wings will extend again if you are not touching the throttle!
The speed is configurable by changing the part that says if GetEntitySpeed(veh) >= 100 then change the 100 to whatever speed you would like (the speed is in metres per second so keep that in mind)
In order to add another model or change which one is used change the config section in c.lua
@XTheGreatJamesX Could you put this on GitHub? I’d be interested in making a pull request for this as I see some potential for improvement but don’t want to be clogging up the replies here.