You can stay tethered while it downloads
I am talking about TWO different phones - and I do not have another USB data cable to use for the other Tbolt - and I believe the ADB process - won't know which device to use - so it will not work. I cannot see how the USB fake Ethernet connection of Easy Tether won't confuse the ADB process when it looks for attached devices.
I found this one => x/xxxxxxxxx/Stock-ROM.zip , BUT I do not know if it is 605.3 or 605.9 or if it is yours. [actual link edited to be removed]
I will have to use that slow 384 kbps (maximum) link - and it will fail on that large of a file - or take hours to download.
I am unrooting because I beleive this phone's first attempt to root used the wrong bootloader option in the tool - it was a 1.04 loader and I selected 1.05. The tool halted and failed after getting root and trying to install it - then I realized I had selected the wrong bootloader option - I restarted the process - and I cannot remember if selecting 1.04 or 1.05 the second time around got it to finish.
BUT - it ended up with screwed up WiFI and Bluetooth - the persistent "WiFi error" - where the WiFi had worked before.
Nothing has a possibility to fix it but to match the boot and kernel files back up before rooting and installing a rooted ROM I believe.
See
Solve Your Sensation WiFi Problems and Learn More About HTCDev Unlock – xda-developers
I know it is a Thunderbolt and not a Sensation - but the WiFi Issue and the bootloader issue is the same issue for HTC period I am sure. Knowing Linux - it is the same for all Androids as well as Linux too - I am a Certified Unix Engineer and have worked with my share of Linux for years - and have found this issue on straight Linux too.
I have 605.9 on it now - and was going to use the manual hbooteng.nb0 method - but your tool would be "safer", since it was used to root it.
Besides - I am pretty sure your instructions say - somewhere - you need an Internet link that is NOT a phone.