Welcome Buffalohump! It seems like everyone has supplied you with good advise, so I don't have much to add. Of course, that won't stop me from giving advise anyway.

What sort of elevation change will you be dealing with? Will it be very steep or more gradual? I don't know what sort of shape you are in, but excess gear weight is brutal in the mountains. Definately replace the Otter box with ditty bag(s). Will you be using a sleeping pad? Closed cell foam or self-inflating? The self inflating are comfy, but the weight is a killer. Thermarest makes a great 14oz z-fold pad that is much better for hauling up a mountain.

Don't cut vital gear just because it's heavy, but definately take weight into consideration. Better yet, load up all your gear then start climbing stairs.

-Blast