I guess I was a bit naive to think that marbles to reduce the vapor space was a unique idea. Here's my mead after transferring to the secondary (8 weeks in primary).
The glass marbles are pretty easy to use. Sanitize and drop in to fill. I think it's best to insert as many as you think you'll need first (before the mead transfer to reduce splashing) and while the carboy is on the side so they don't drop hard onto the bottom.