3.4.1 should work just fine, however you'll need to specify the version number with -n 3.4 on the elevator.py command line.
I Elevated a radio with that configuration just yesterday. If you have a spare radio and test AP on-hand (and it sounds like you do) you can follow the manual steps to configure/retrieve the configuration file from the device as per this post's 2nd half
When you retrieve the config from the downgrade d device filesystem, it'll be called .configured_3.4 or similar - the number after .configured_ is what you need to pass to Elevator to make it work.