The way i did it, was to save each project, along with the kit or kits (All sounds are supposed to be contained within a project when saving, but it does not seem to work for sounds that are not stored in a kit).
Then SysEx dump them to C6 (dump whole project or whatever it’s called). Each file should be around 2.2 mb.
Then import “whole project” on the second A4 with C6 and save as project.
Also, see this post:
It’s tedious, but it works, and it’s nice to have a backup of each project on pc.
I store the backups on Dropbox. In case I’m touring and my A4 stops working, I can theoretically borrow another A4 and keep going. Luckily this hasn’t happened yet