I got the second one apart this weekend. This one was a lot easier than the first one.
I did the same thing, grinding the spot welds out, but this time took a little more care about where and how deep I went. Then, when I saw the black lines appear I stopped.
Then I stuck it in the freezer over night, took it out the next morning and used a BFH (bigger than last time) and a little heat and it popped right out. Much easier.