The Disc-Hugger is very similar to the old frames, but there have been some changes. Still wanting to keep it all as light as possible, the new frame features Velcro the entire length of the frame where it attaches to the inside of the bag. The old frame can come loose on the back at times and slips down into bag. Not a big deal, but pissed me off. Then, to keep the bag open from side to side and to HUG the discs, I added 1 ounce of fiberglass rods inside the large rectangle. The weight of the bag pulls them close together and hugs the discs. When you pull a disc out or push it into the bag, there is a slight 'snap' along these rods.
It just improved the bag by leaps and bounds.
Will it fit the old bags, yes, but the old bags lack the full length of Velcro to hold the frame in place so it could come loose. I will get pictures up on the site next week.
I am possibly interested in getting a new Disc hugger. I haven't had a problem with the old one coming loose, I could always use sticky sided velcro if needed. I like to have the latest and greatest, but the next bag purchase will be a crunch box. This might be a cool way to upgrade my bag without the bucks of a new one.