iOS GameCenter - testing non-live achievements and a live leaderboard

Question

I have GameCenter integrated into my application, as I have a leaderboard that displays user's top scores. I published my app to the app store, and then decided that I wanted to add achievements.

However, from in-game, it seems I can't view these achievements, as, the only way to test it seems to be to sign into a GameCenter account (which I did) and view the leaderboards/challenges/achievements. However, since the leaderboards are live, and the achievements are not, the achievements do not show up.

I tested this by creating a test application with a non-live leaderboard and non-live achievements, and the achievements did indeed show up.

Is there any way I can resolve this without just publishing the achievements to the app store so they go live and hoping they work okay (a terrible practice which I would really rather not do). I've contacted Apple already, but in the meantime, was wondering if anyone had any recommendations? I've heard a few things about Sandbox testing, but I tried making a sandbox GameCenter account and that didn't seem to make a difference, although I'd be open to any suggestions.

Thank you.