I've been meaning to buy a PnS for awhile now because of the convenience for the fun shots, but I haven't. I manage with my 20D+Grip just fine. I bought a hand strap so I don't have that long annoying neck strap, and it doesn't give me a back ache anymore. It's very easy to walk around with, the camera just hangs with your arm nice and easy, and doesn't require you to grip it tight the whole time - the strap rests against the back of your hand.
Now, as for Everest Base Camp, my sister hiked to there a few years ago and I've wanted to go since. But, unlike you, screw the macho image and hire porters for your stuff. They love the income, it's easier work for them than what they'll usually be carrying, and then it's just you and your camera - You won't miss those shots if all you have to worry about is your camera. Make it as painless as possible to pull it out, or have it out at all times!
Sadly, I think your neglect to hire a sherpa is the root cause to the lack of all your pictures.
Now, as for Everest Base Camp, my sister hiked to there a few years ago and I've wanted to go since. But, unlike you, screw the macho image and hire porters for your stuff. They love the income, it's easier work for them than what they'll usually be carrying, and then it's just you and your camera - You won't miss those shots if all you have to worry about is your camera. Make it as painless as possible to pull it out, or have it out at all times!
Sadly, I think your neglect to hire a sherpa is the root cause to the lack of all your pictures.