We are going in 2013 too.
My crew will be struggling with this too soon.
Eliminating the volume seems to be the goal, the wt will take care of itself.
The philmont gear IS heavy, but is still only ~3 lbs per person when split up, so the wt alone seems to be not an issue to me. ( unless you are the poor guy that gets stuck packing the "wet" 4 lb dining fly that now weighs 8 lbs.)
Some crews have successfully used light wt packs, so it seems it CAN be done.
On my Circuit, i put my down bag in first, then a 1 gal ziplock with a few spare clothing items (socks, beanie, glove liners, synthetic tshirt, longjohns), then puffy jacket and 100 wt fleece, then squeeze down and wrap up the liner. When compressed down the compartment is only maybe 1/3 full. I have easily 2/3 of my pack still available for food and a 2-3 lb share of crew gear, + room in outside pocket.
Outside pockets hold water bottles, tent, raingear. hipbelts hold miscl small things. Of course the tent is pretty small.
I cant imagine not having enough room for even 6 days food. I could fit a bear can in there. It all depends on what else you are trying to bring , and how bulky your personal gear is. If you want a small UL pack, I think a highly compressible bag is a must, along with light and thin insulating gear. Things that cost $$$ unfortunately.
Another key I think, is to have the scouts tenting together in large multi-man floorless shelters(a groundsheet counts as a floor) instead of conventional double wall tents. That saves a tremendous amount of volume and weight. 4 people can sleep in single mid that weighs 25-30 oz including plastic grounsheet and stakes, for a wt of 7-8 oz each, compared to 2.5-3 lbs each for conventional 2 person tents. Only one guy needs to carry the tent though, making room for others to carry bulky gear. Or bulky food.
I second that no adult leader should be carrying a bunch of gear "just in case"
oreven because a kid doesnt have room. It is a crew trip, boy led. As in all scouting things, the adults are not there to carry the the boys, they are there to "advise" and facilitate, (and maybe keep a watchful eye on them.)