Sorry for so long in replying. Tails is a relatively hardened Linux, there is not an electrum.exe on the system. I compiled the executable from source code, and store an MD5sum checksum of the executable in another location in the encrypted storage. It takes 10 seconds to run md5sum  /path/to/electrum so that I can verify it is exactly the same one every time. The Tails USB stick's main use is for bitcoin, no casual browsing, and never any personal email/social networks, etc. I am confident in my ability to use it without getting malware.

My goal was to have a portable USB OS to be as secure as I can make it, to use with Bitcoin. At the same time, I don't want to have a One, Vital, Important Stick That I Cannot Lose.  I image the stick with the dd command (from another running and secure Linux), and can make one big file that I can recreate the USB key from. I have many of them in different locations. If I do lose it, the encrypted parts use a very long password. If it's lost, I have only lost a few euros worth of USB stick, not my information.

My interest in using .onion/Electrum servers is not because I am working with any large amount of BTC at all (to the contrary!) It is just part of this ongoing experiment in making it as secure and private as I can.