I was all set on getting the Citius Remex, but my son's puppy visits regularly, and the C/R looked like it might make a fun and expensive chew toy for him. So I purchased the "Perfoarmance Rowing Seat Top" from Revolution Rowing, and it showed up a couple of days ago. Installation is a bit different than the Concept 2 seat, but I used wood screws in the carriage mounting holes, and it seems sturdy enough for now. The C2 seat has threaded sleeves that accept bolts, which I can try to replicate should the current installation fail.
I installed it today and gave it a 5K spin.
Impressions:
1) Its footprint is smaller than that of the stock seat, a half-inch narrower and 2 1/2 inches less fore/aft ... maybe a touch thinner, but the topography makes that difficult to quantify. Both rollers protrude, but it didn't create an issue for today's row.
2) The "curviness" of the seat is more pronounced. I see this as a good thing, since more of a cutout in the back is what I sought.
3) I'm not sure I care for the amount of upward flare beneath the legs. I suppose it's a necessity to get the depth that people want for relief of the sitz bones, but I was OK with that part of the stock seat design. I hear that for many, the amount of depression is the particular issue they hope to address. As for me, I had to adjust a few times, so it wouldn't feel like it was applying pressure to my hamstrings that would become bothersome.
4) Overall, I think I'll enjoy the change. It took a few minutes to get to a position I was happy with, but it was dialed in within 1,000 meters and felt good for the rest of the row. I assume as I use it more it will be much quicker to find the "sweet spot." If something alarming comes along on longer rows, I'll speak up.