You have plenty of rudder authority with standard rudders airborne and I have demonstrated landings of up to 22 knots direct cross wind (varsity day for me though!). The large rudders do two things----they look cool----and they get you rudder authority quicker on the takeoff roll. The quicker rudder authority will let you get off the ground quicker in a crosswind (don't have to drag a brake as long to keep the nose straight). Converting to the larger rudders is a good first project for a new owner since it is relatively an easy foam and glass job. It should take about a weekend to do----then you need to add paint. You can buy the plans off the rutan website (about 15 bucks I think).