I have the same problem, i need help because i investigate a lot but don't know what to do now exactly...If you go Hp, they ask you for 300$ motherboard.
I Everytime stucked at 0,1% : I Try a lot of HPRompackage,
Modified rom, modified installer Hpruu, etc..
The Rom dump via d2s : doesn't include the gsm parts
We need arguments and specify a adress range :
if you want i have a radiorom dump of the
Adress : d2s 60000000 800000,
and the radiobeetlespatch.
But i don't know exactly how to investigate more the good adress.
I think we have to delete and rewrite manually good adress range.
I can find you a lot of rominstall to change language,
( not the problem just modifications in nbf files with winhex)
I investigate a lot the bootloader, have password pass 1, etc...
Try to listen with Usbmonitor, look dump of ram memory with winhex,
etc... So a lot of way to investigate and a lot of solutions for other device very close to our 6515.
So I send to everybody ask me a complete packages of the tools & rom who can help, and my extended info.