Trouble downgrading G900V from 5.0 to 4.4.2

Currently running 5.0, kernel 3.4.0, build LRX21T.G900VVRU2BOE1

I attempted to flash a few ROMs unsuccessfully, eventually realizing I need to downgrade to 4.4.2 first and gain root. That is failing as well. I have the stock 4.4.2 ROM from sammobile (G900VVRU1ANE9_G900VVZW1ANE9_G900VVRU1ANE9_HOME.ta r.md5), but this is what I am seeing in ODIN:

<ID:0/003> Odin engine v(ID:3.1005)..
<ID:0/003> File analysis..
<ID:0/003> SetupConnection..
<ID:0/003> Initialzation..
<ID:0/003> Get PIT for mapping..
<ID:0/003> Firmware update start..
<ID:0/003> SingleDownload.
<ID:0/003> aboot.mbn
<ID:0/003> NAND Write Start!!
<ID:0/003> FAIL! (Auth)
<ID:0/003>
<ID:0/003> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)

Am I missing something? I have gone through countless threads but nothing seems to pan out, just another tar file that fails. I am soft-bricking the phone each time by the way, but recovering from that is not an issue.

Thank you