Look, I know a woman who shoots owls while humping a Canon 500/4 through the woods. I mean, that is dedication to the art, as we are talking about 8-10lbs worth of lens and whatever the camera body runs. I mean is you have the will-power to do it, great! Personally, that's serious work, as you tack on the miles.
Remember the short, Diffractive Optic 400/4 that Canon produced?
It was a backpacker, for sure. Priced accordingly. It was definitely lighter.
Again, the 300/2.8 is a serious lens... and I applaud its capability, just not its portability.
