Both the GS II and G4 now come with the intex II frame. Am running both. My GS II is the older version from before the advent of the Intex frame. It's a smaller pack than the operator, and while the frame would be nice, it's not a deal breaker for the GS II. I do have an Endo frame that I have lashed into the GS II which provides some rigidity.
Both of these packs work well and I personally have no complaints. Some will say they are heavy compared to other similar sized packs, but I equate this to the tough, sturdy construction and it's not a negative to me. Each will carry your rifle well. You just have to determine how much gear you want to organize and hump, then pick accordingly.
If you have any questions at all, contact Ceylon - a hide vendor, at DeltaOutdoorsman.com. He's the resident Eberlestock guru and has probably forgotten more about these packs than most of us will every care to know.