I'm in the middle of building Warren's 29" singlespeed, using my usual Paragon sliding dropouts, and I thought I'd post a couple of pictures, partly because I told Warren I would, and partly because I have had some inquiries from framebuilders about how I go about welding them in (they're usually brazed with 56% or nickel silver).
If you're interested in why I use these and not EBBs, you can refer back to the faq on waltworks.com. Suffice to say that I generally dislike EBBs, and I like the Paragons a lot.
In any case, the main issue with the Paragons is heel strikes on the chainstay - because the actual dropout sits inboard of the horizontal slotted portion (where the chainstays and seatstays attach), the rear end of the bike is effectively about 10mm wider than normal. Throw in the fact that the dropouts are LONG (so the stays reach their maximum width closer to the bottom bracket than they would with a normal dropout) and it's like having chainstays that are 15-20mm wider than normal. So to minimize this, I slot the chainstays way outboard, so that the chainstay sits a little inside the dropout. Second, I like to use the Nova cycles s-bend chainstays - normally, s-bends tend to be for show more than anything, but in this case, they really help keep your heels from hitting the stays.
Here's a picture of the whole rear end.
And here's a closeup of the dropouts and stays - it's a little hard to tell what I'm talking about with the offset, but if you look carefully you can see it.