OK - thanks. I'm still doing it manually but will probably also use Llama to automate it when I get a chance to play with it. Am on CM10.1 also.
Right now I'm using llama to automatically switch to 2g when the screen goes black and switch back to 3g when the screen turns back on. It's stable since then and I can live with that setup. I'm still eager to try relocking the bootloader though, to get rid of that extra app.