Managed to get an hour+ on the trainer with the new saddle.
Needs a little work - not as comfy as my Pro with 6 months of riding on it, but it feels wide enough, and I like the narrow nose, with the aggressive sidecut. When riding the Pro in the drops it always looked and felt a little tight between the legs. (I'm now considering cutting the Pro - although it is now properly mounted on my touring / commuting rig, with a more upright position)

The Swallow has much longer rails. I eyed and mounted the saddle too far back - and as I warmed up my spin felt all bouncy and strange. (I checked the height and it appears to be the same as the Pro - so I didn't quite know where to start adjusting) I watched me knees as they came around and noticed that it looked like I was significantly further behind the pedals than on the Pro. After sliding forward a few times, and making some adjustments, my legs felt "normal".

I rode on the hoods and in the drops at a tempo pace for about 1/2 hour. Everything felt fine, if a bit stiff. Warm up and cool down was done on the tops and hoods. After 1 hour I started to feel some soreness on the sit bones - nearly the same feeling as I broke in the Pro.

I may tweak the fore aft position a bit, and I'm not sure on the nose position (up a bit or level). Initially I think it is going to work... but time will tell. How I feel after 1 hour may be very different from 3, 4, and 6.

More later... as I get more time into it.