Thanks for the tip about adding a second shoulder strap!
I gave the slingshot a try yesterday on a 5 hour hike through the Hilton area of Patapsco River Park near Baltimore (Maryland USA). The autumn leaves are really starting to reach peak color, so I didn't want to lose the moment. The area is hilly and the footing at times can be a bit dicey, especially with fallen leaves. I fully loaded the bag with everything I own, and it ended up being pretty heavy, maybe 25 lbs (plus?) Anyway, the first thing I noticed was that the hip straps are the key to getting the slingshot comfortable on one's shoulder. Once I cinched them tight around my waist, the pack was comfortable and secure. I felt stable on rubble-rock footing and when hopping around the banks of streams and over slippery rocks. With tripod attached, it is not all that easy to get the camera out of the bag when it is on your shoulder, but I pretty much keep my camera in hand, so this is a major problem for now. I ended up with some nice shots, and I am especially happy I brought along my tripod, which was a major selling point about the 302. All in all, I think I made a good choice in this bag.