Lighter wing load= more lift / lower stall speed.

In other words , you have to maintain a higher airspeed in order to prevent stall.

Not necessary that top speed will increase.

A heavier model won't fall to the ground any faster.
The next time you attend an amuzment park , flick a coin out on one of those drop rides, such as the super man.
You'll see the coin float. I forget the name of the guy the dropped a couple of marbles off a tower a couple of centery ago.
Bascailly you're falling at the same speed, that's why you'll see the coin float.

less drag = more speed
more power= more thrust