Mini-update:

The Origin8 seatpost failed. It's such a chunk of garbage - I'll never buy another from them. I ordered it online from a US vendor, so it's not worth trying to get a replacement, I'll just go buy something good locally.

The failure was with the clamp that holds the seat in the correct position & orientation. On my 2nd ride, when leaning back on the seat, the rear dropped, causing the seat to point upwards. I pulled over and adjusted it, making the clamp bolt a bit tighter this time. It was OK for a few days, then did the same thing. Again, I made the adjustment and increased the torque as much as I was comfortable with given the size of the bolt. On Saturday it did the same thing yet again, and when I tried to re-torque the clamp bolt, I could feel that it had stripped. Luckily I wasn't far from home, and I can use the exercise of finishing a ride entirely out of the saddle.

Of course, I could have done something wrong, but I've installed & adjusted quite a few saddles on quite a few seats of varying price & quality and have never had this problem before. Put me down as an Origin8 h8r from now on.