Would it be possible to downgrade to the official shipped Sprint 1.56 ROM (RUU_Hero_C_Sprint_1.56.651.2_signed_release.exe) from official 2.1 ROM using recovery-RA-heroc-v1.6.2? I know hboot was changed in the latest ROM and 1.56 RUU generates the dreaded 140 error, but would it be possible to extract rom.zip and flash it using RA?