If you are anything like me, a camera buried in a backpack will result in fewer photos. Much of this depends on your shooting style. Are you taking a tripod?
Not sure if the Pentax will fit in the Clik chest pouch. There are three sizes
here. I've been on the Harding Ice Field in Alaska, climbed several peaks including Mt. Rainier, and saw my feet just fine. I don't think I stepped on the rope even once! :-)
I put the camera in a chest pouch with a small lens, then put the extra lens(es) in the backpack w/ tripod strapped on the back. I don't think a hard case is necessary, with one caveat: If you use a soft case or wrap lenses in something soft, don't attach the lens hood reversed. This can put quite a bit of stress (torque) on the end of the lens when it is packed away in your backpack. Instead, just put the hood in but not attached, or put it somewhere else.
If you are religious about getting the tripod out for every photo, then stow the camera; the added effort of getting the camera out is almost nothing compared to removing the backpack, taking off the tripod, then putting it all back together. Another consideration is short day-hikes while on your trip. You may stay in one place two nights and want to wander. That would be tough with a hard case; you would be stuck carrying your whole backpack or hand-carrying the camera. Chest pouches are great for this. I find those situations represent the best photo opportunities aside from early morning / late evening at camps.
The key to the chest pouch is to rig it so it clips into the shoulder straps up high. This transfers the weight to the pack so the whole thing isn't weighing on your chest. Makes it feel like it is
almost not there.
Dave