@armed_zebraI just bought a new (old stock but 0 miles) 2019 SP from a dealer. I had seen this thread and the other one (thread named "SP Passenger?") and was doing research because my wife loves to ride with me. Most info was that the left side holes for the passenger pegs were not threaded and that the rear seat wouldn't latch properly. I bought a seat and rear foot pegs from ebay before even taking delivery of the bike.
When the bike showed up, I was surprised to see that 0 of the 4 holes for the pegs were threaded. No big deal, I bought a whole bag of 10 time serts but what happens when someone wants to high mount an exhaust? They have to thread the hole themselves??
Next was the seat. Its an OEM Honda part and it snapped and locked right in without a single modification. Fits and functions just like it should on the base model. Pretty stoked about that! It didn't come with the strap / handle so I don't know if that has anything to do with it. I would not have installed that anyway.
Just wanted to post that in case anyone else was looking to add a passenger to a 19 SP.
link to the time serts you used?