If you're going to rent from LensRentals, have it shipped "Hold At Location" to a nearby FedEx Office location.

My vote is the 600/4 and a 1.4x. 840/5.6 is a really nice punch for long shots (better than the 800/5.6 and still lighter than it too), while keeping the 600/4 option for when the sun isn't so high. Or the 400DO II if you want some amazing portability (aside from size) - I don't know about the II version, but the old version I think had "inverse" chromatic aberration, so it took a 1.4x really, really well. Or for something a little different, try the 200/2 and a pair of TCs; 200/2, 280/2.8, 400/4 is super-cool, and the 200/2 will blow you away.