Got H+ on Net10/AT&T
I used DFS (from cdmatool.com) & dev drivers from somewhere on XDA to set NV item 8322 to 0, and now I have H+ on Net10/AT&T in the US, with the US modem. Still says "Sim from unknown source" on boot, and remember set your APN correctly. Please report if you get this too, maybe there's something else I changed that is also important.
Super thanks to CellZealot, P3Droid, and everyone else for investigation, I wouldn't have tried if you didn't.