M_Boats: Trailer Extension

I'm wondering if I should extend my trailer extension on the ramp or extend it when I am rigging the boat (M 15) and back down to the ramp with it extended. I rig my boat on a flat parking lot about 20 feet above and 200 feet or so from the water. As I only launch my boat once a year so I don't have much experience. I've done both and have been nervous both times. Thanks for the advice, Willy Gorrissen Lula M 15 606