The 3.75 lb. weight is the minimum, not the maximum. However, all things being equal, the lighter plane will win every time.
If you are using standard servos, you may want to go to minis with the same (or better) torque. The minis are about 1 oz. lighter per servo (3oz.). The next move would be a 350 NimH battery which weight about 1.2 oz. (2 oz. lighter than a 700 Ni cad). Those 2 things would save you 5oz. and put you right at the minimum weight for 424.
I actually use 2 cell lipolys now, and use a 6volt regulator to increase the servos power and speed, as well as the light weight of the lipos allow me to carry more milliamps.
Good luck,