just my opinion, but 5lbs is a lot of extra weight.
for prevention of altitude sickness I would look into getting some diamox (talk to your MD).
a few little pills are going to weigh a lot less than a 5lb cannister and will likely be much more effective.
Proper acclimitization is your best bet. A night at the portal followed by a night at Lone Pine Lake would be great. Or head over to Horseshoe meadow for a couple of nights before the hike.
When I got altitude sickness, the symptoms went away very shortly after I descended a few hundred vertical feet.
