The WRAP lacks a USB port, so the keydrive is not an option. I don't mind writing to the CF, but it wasn't working for me: the changes I made would revert upon reboot. Found a hint on voip-info.org that I'm trying out. It says to make the changes to the conf files in /etc/asterisk/ AND /stat/etc/asterisk/ while in read/write mode.
After a week using AstLinux on the PC Engines WRAP, I like it a lot. This will make management much easier, while keeping the energy costs down.
Another week goes by and I'm still happy with Astlinux. I'm very pleased with the utter simplicity of the setup. Kudos to the devs!