You may want to try Rockbox for this.
It’s not currently supported for the v2 Fuze but the dev version is now working quite well and I don’t think it will be too too long before it’s a stable build.
I tried out recording and it’s working.
On Rockbox you can choose which directory to be your recording directory and so you can choose one on the microSD card. It also give smany options for recording format, frequency and modes. Many options there and a recording meter too.
To choose where recordings are saved just browse with File browser and select directory. Then hold down center button until context menu shows. Select option “Set as Recording Directory”.
