I have decided to be a lemming and get frame bags for my mountain bike. I did the GDMBR with panniers, and they worked fine, but there is little singletrack on the Great Divide Route. Idaho Hot Springs Route, however, has a lot of single track, offered as options. It is pretty significant, so hence the frame bags.
Revelate is the brand I am familiar with, so I bought a frame bag, the harness, a gas tank and the Terrapin seat bag with a detachable Terrapin dry bag. I got a second Terrapin dry bag to put my tent in on the handlebar harness (Revelate states that dry bag will serve very well there). My bicycling partner bought the SweetRoll and the Viscacha seat bag, which has a dry bag as its main component. This is kind of cool, since we will be able to compare the two systems.
In addition, due to the high elevations, I bought a Big Agnes Q-core air mattress, which offers some insulation, unlike my old thermarest. We shall see how fast I get tired of blowing the thing up.
I have decided to buy a lighter, smaller raincoat, since I think we will see little rain. Going with the Novara Stratos 2.0 Bike jacket. REI was unable to give me a weight on it, so I will have to weigh it when it arrives.
And I bought an Osprey Manta 25 backpack off of eBay. Fool of a seller took out the hydration pack's stabalizing stay, which I tried unsuccessfully to re-install. I am pretty sure the stay's purpose it to keep the bladder from sagging, keeping the weight of the water evenly distributed from to top to bottom. Calling Osprey resulted in an invitation to send them the pack. I pay shipping there, they fix and return to me on their bill. Lifetime warrantee. The pack seems really nice, with enough room for stove, kitchen and food. I plan on hanging the entire pack (from bears). The hydration bladder seems really well thought out.