Pierreyves,
The tailpiece on my SC Standard isn't symmetric either, but you know what? I don't care. Yes, Alembics are expensive. Yes, they're handmade. But because they're handmade, those tailpieces are fitted where they will perform as designed, not where they'll look the best. Speaking only for myself, I'd rather have a tailpiece that's positioned for performance and playability and not symmetry.
Frankly, I could care less how it looks - what matters is how it sounds and plays. My SC plays and sounds great. That's good enough for me. Besides, I don't think the Symmetry Police are going to notice and arrest me.
Shim,
I bought my SC Standard at G-Cat, and can vouch for their work. They are located off Line 6 of the Seoul Subway, Sangsu Station, Exit two, about 400 yards down from the Subway entrance. I'm in Seoul should you ever care to converse or share Alembic stories.
My two cents,
Alan