I have my HD500 in my old XTLive bag and it works ok, but is snug. I tried it in my X3Live bag, and it did not work at all -- plus I still keep my X3L in the car at gigs as a backup to my HD500. The X3L bag was needed because the X3L was wider (side to side), and less deep (front to back) than my XTL. I remember being disappointed that I had to buy a new bag when I moved from my XTL to my X3L -- was hoping they would have kept the same form factor. When I bought the HD500, I experimented with the two bags, and found the XTL bag to fit the HD500. I think you are right though that having hauled my XTL around for about 4 years probably did stretch it out enough to make it useable with the HD500 - closer to thre XTL size than the X3L, but not exact. I was bracing for having to find a new bag once again when I bought the HD500, but lucked out not to have to. My XTL got fried (power jack issue), so was sitting dead in its case anyway. My X3L is snug in its fit with its own bag, too.

Dave