Weight up front is good, but like Rusted mentioned, you want to get it down low. You also want to have a balanced rig. Too much weight in front is good for climbing, but eventually you have to come down. A moving vehicle with too much weight up front and mounted high, will put you into a tumble going downhill. Get yourself a set of beadlocks, and/or add some weight to the wheels themselves.
On my Frankenstein SCX10, I run Axial beadlocks and I've got 2.5 oz of weight in each front rim, plus another ounce of weight attached to the top of my axle mounted servo, and the battery is mounted out in back. The 1/6 Jeep has the weight in the wheels and on the servo, and running the battery behind the front suspension, but the weight behind where the the motor is mounted is balanced. I have the spare, a battery for the taillights, and the rollcage. The Jeep weighs 13lbs. Both rigs are balanced so that there is equal weight on both sides of the skid.