For the same goal, I that procedure from REWA: https://blog.rewatechnology.com/how-to-upgrade-ram-on-macbook-air/ so it is feasible.
There is one step that isn't that specific, it seems that the BIOS must be changed and restored. At my level, I don't know what version to use. Also there is a few resistance to upgrade.
My Macbook Air 3,2 4GB late 2010 are very exited about the possibility, in particular when the available RAM sinks down to 2-300MB...
'''Jconsole''', did you found out more since you started this quest ?