I was able to get the radio & bootloader to 1.51.00 just fine.
Next step for the DFT_RSPL_WP7FG1_LAUNCH returned the following error:
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[Error Description]:
Invalid ModelID. This means that your phone not supported.
This installer supports only limited number of the phones.
SPARK, MOZART, MONDRIAN, GOLD, SCHUBERT.
If you have phone from this list, but still have this error, please contact with DFT team.
[Info]: USBWorkRSPL.cpp (235)
[Error Description]:
ModelID is 'PC931000'. Please report this info to DFT.
[Info]: USBWorkRSPL.cpp (234)
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Looks like I need to wait until they get my specific HTC Arrive model supported