No lead
I hate adding dead weight (lead) to my planes. Instead try using some of these options:
Bigger battery (maybe go 6v)
brass prop nut (these are much heavier than the aluminum type)
change the prop-APC is pretty heavy, wood is light
Change to heavier or lighter wheels
Change your throttle servo to a lighter one. You don't need a standard servo to operate that little throttle.
Install lights and a seperate battery. There are several brands that run on a regular 9v battery.
Change the engine mount to a soft mount. Its aluminum so its heavier plus the soft mount puts the engine further forward.
Remember, functional weight is always the best kind!