I got 3 also and tried one on a short walk a couple days ago. I put it on my Eberlestock J34 and went for a mile or so. It worked as advertised. I had 40lbs in the pack and it was loaded pretty wide so it pulled on the strap a little, kinda dug in and leaned to the outside if I didn't hold the gun and help it a little. It didn't slide off my shoulder though. It would sure keep my rifle in place while I used both hands to climb up out of a ravine or something. It slid down the strap over time on me, I think the higher it is mounted on the strap the better it keeps a rifle in place. I think I will modify the attachment just a little to keep it up higher and leave it on the pack for good. The main thing I was worried about was it slowing me down getting the gun into shooting position. For me, if it was mounted a little low it never interfered at all. With it mounted higher where I plan to put it, I had to adjust for it just a little. I think I will shorten the retaining hook and then it won't catch at all.
Bottom line, I like it especially for a wider pack like my Eberlestock. I never liked carrying a rifle on a sling with that pack before but it wasn't a big deal since I usually have it in the scabbard anyway. I will post again once I try one on my little Camelback Stryker that I use when going light and carrying my rifle slung.
