How big is the papoose in its case? The reason I ask is because all 3 of my backpacks are 18 inches tall, and my AR7 fits perfectly.
I never had the POI issue that you experienced, but sometimes the front sight will shift if it touches something and you can't hit a thing. Lost a grouse last year to that. Now I make sure every time I put the barrel on, and before I shoot to check that it's in place. I may just glue it on there so I don't have to worry.
Maybe I'm just an AR7 fanboy, but after about 5 bricks of ammo I've never had a jam and only one FTF, which went off when I put it in my JW-25a. I'm using CCI Blazer.