My Sig Kougar is 6lb (after I put it on a diet) the upper limit of the kit recommendation. Before, the airspeed needed to be high to keep it flying and it had to land way to hot because the wing loading was so high. It flys fine at 6lb but if I could shave another 8oz off it it would be much more crisp flying and land slower.

Shaving 8oz off doesn't seem like much, but for a 6lb plane that's 1/12th it's weight. If you shave 1/12th the weight off someone that's 180lb that's 15lb. So small amounts of weight can make a huge difference as they add up. 8oz is probably the extra coat of primer and paint I put on it.