FWIW...lesson learned the hard way..
The family just came back from a trip to shoot Tigers and other wildlife in Central India. All shooting done from Safari Jeeps.

I asked about taking the 500vr on several forums including a couple of Indian forums. Consensus was that the 500vr and a Beanbag was really worthwhile.

So after lugging the lens on two flights to get there(with gear for all three of us) I found that very few of the jeeps were configured for beanbag use and we did not get one on any of our trips. Also in India driver and Guide are mandatory plus how ever many shooters.

My understanding is that most safaris now are from vehicles only(I do know there are exceptions in Africa).

Word to the wise...try and find out exactly how your vehicles are going to be configured. The 500vr was only taken out once and not used(Driver, Guide and 4 shootres maxed out the space). My eight year old was the only one that could have used a beanbag because he is short but he did not need one for his D40x and 70-300vr!
Cheers,
Tom

T.D.Hardin
http://taja.smugmug.com/
http://images.nikonians.org/galleries/showgallery.php/cat/500/ppuser/165169