This ↑↑↑

No.

It will result in constant rubbing between the stem and the spacer under alternating vertical loads. Wear is probably not an issue, but it might result in a variety of annoying noises.

Also, that single hot contact point will determine the preload of your entire headset. That is not sustainable to any meaningful degree.

Why buy a stem like this? Return it for a 3T, Ritchey, Deda, Bontrager, whatever.

For 2 reasons:
1. Zipp stems don't have cutouts and are therefore better for carbon steerers (do a search for Luescher Technik).
2. I already have Zipp Quickview faceplates with integrated Garmin holders.

https://cimg1.ibsrv.net/gimg/bikefor...1d237b05a0.png
The Zipp stems are cut out on the inside.

Don't be fooled by the stock photos. The cutout on the steerer clamp is actually much smaller (I wish other manufacturers would do this too, but I guess saving a few grams on paper is more important)


https://cimg1.ibsrv.net/gimg/bikefor...4b73f9d4db.jpg

If you are that concerned with delaminating your steerer, why would you use a stem that puts uneven pressure on the headset split ring?

I'm NOT using this stem. Why did you think i was using it? I'm not the OP. I've bought several but they are brand new and I'm selling them precisely because I don't trust them with even pressure. But I got curious when the third identical stem I ordered had the same issue and tried to search for it. That's how I found this thread.
I'm using the cheaper non-SL Service Course stems, which are slightly thicker around the clamp edges and properly faced.

That was the rhetorical "you", as in "Even though you like this one feature that protects your steerer, why would you or anyone else ignore the feature that might damage the steerer in the process?"

You are the one that answered my post why anyone would choose THIS stem, not some other stem.

We were having a dialogue, so I took your "you" to mean "me" :) This stem seems to sell well, but I have no idea if most other people buy it for the same reason as I or not. I would buy it for the minimal cutout, but I think it has a major flaw. I've had many stems (Easton, Answer, Syntace, S-Works, Giant, 3T, Deda), but they were all properly faced. And so is the cheaper 6061-alloy Zipp Service Course. With the SL version, I think they wanted to reduce weight without making large cutouts (which I approve of), but then their only option was to make the steerer clamp a bit too thin and tapered at the edges, which resulted in this issue (though I guess they could still have faced it better)

i'd try facing the stem's bottom side...

find a fork with a factory cut top... slip the stem onto it upside down... leave enough of the stem to clean up the uneven-ness hanging out past the top of the fork steerer, then clamp the stem onto the guide fork... file or grind to a flush surface with the factory-cut steerer....
i will be doing this to the stem on my fuji soon. :D

That definitely sounds like a reasonable step, but it's what the manufacturer should be doing ;)

grousing won't fix a thing.. but careful grinding or filing can. ;)

somewhere inside the Zipp Factory, a stem prep finisher is in need of further training.
"Do NOT Sand away the Working Surfaces!"