Very nice. I just bought the same lens but have yet to receive it.
Is the point of the beanbag that it allows you to shoot from inside the vehicle, should you require a hasty exit? I can imagine a few of those scenarios on safari.
You can't leave the vehicle, otherwise you would be breakfast. Space is limited so the beanbag allows you to use the edges of the safari bus as a stable base. There were only two of us in the bus but if you were in a bus with 7 others there'd be no space for manouvering a tripod. I didn't find a monopod stable enough, the 150-500 is a heavy beast.