You need to factor in the increased thermal speed and larger diameter circles. Unless the core of the thermal is large the climb rate is reduced significantly more than just the glide calculations predict. In the "real world" higher wing loading gives an advantage, but not as much as many think unless you are flying mostly on streets. In the mountains I often do better with a 9.5 to 10 pound wing loading because I can maneuver better and work small diameter thermals.