Well, I have to tell you that it really might benefit even the little loaf tester.
I have made soap with it only three times so far and it does sort of want to come loose when moving it. Granted, I learned I should keep it on a stable movable surface and not actually pick it up on it's own when it has not-yet-set-up soap batter in it. But sometimes a soaper moves the mold a bit this way or that to get a better angle for a swirl.
The last soap I made in it was a rimmed soap and I like how it came out. But I did notice that sometimes leakage can occurr. I had that happen with the rimmed soap. The batter wasn't even that liquidy by the time I poured it because it was the last of 3 molds I used and the color mixtures had begun to set up before I started filling this mold. That's why the center is so plain looking. So I'm pretty sure it's because the seal wasn't secured. Of course the rim pieces probably helped push against the interior, so a strap would have helped in this case.
Here's how that one turned out:
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