Not sure if it's strictly recommended but the outriggers should be strong enough. If there arent' they probably neede repairing anyway. You could always move the jack closer to the central back-bone tunnel of the chasis to reduce the strain a bit if you're worried.
The ends of the outriggers immediately behind the front wheel and in front of the rear wheel are usual jacking points. I'd personally always stick an axle stand or similar under part of the central ladder section as insurance.