Doc4570,
The Savage 24's are nice (I am a sucker for anything in two caliber's) but since he was interested something specifically for backpacking, I don't think these would apply here due to their size and weight.
I don't know how much experience you have with the .410 but most people are always putting it down when they rellly don't have much/any experience with it. I happen to like the .410 and use it for both hunting and clay birds. The .410 shoots its paylod at the same speeds that the 12 & 20 do, it just shoots less payload which means you have to be more precise with it. I can easily limit on dove and qail with it and regularly break 21-23 on the skeet feild with it.
Sherman,
I am biased for the M6 since I have 3 of them. For your purpose I think that the M6 would be great. The only thing the papoose gives you is slightly quicker (you can be pretty fast with the M6) follow up shots. Other than that you don't have the shot shell ability of the M6. I can also tell you (being a backpacker also) that the M6, when broken down is a very slim package. If you want a little more ooomph, then get the .22 Hornet /.410 M6 and then you have a more powerful centerfire .22. I have both but would reccomend the .22 Lr since ammo is cheaper and you can carry alot becasue of its size.
NJW in AZ