Yes you can run the OS as a pusher or puller.

Running in a pusher configuration, you don't get as much air flowing over the head to cool it as you would with a puller. These nitro motors are designed to have the prop wash flowing over the head to cool the motors. So if you don't get adequate cooling, your motor runs warmer. Which will lead to shorter engine life and a loss of performance.

If your gonna run a pusher, boost your oil content to 20%. Fox fuels carry fuels with 20% or you can add castor oil to the fuel to boost the content.