I flew a TriPacer last summer and found the sink rate quite acceptable. It's not a lot worse than the 172. I could not stall it at any power setting, but there were no pax in the back seats, either. At full power and full aft elevator, it actually climbed. I did not think at the time to run the trim full nose-up to see if it would stall, since the trim adjusts the stab and would give more nose-up authority. I wanted to stall it so I could spin it. The POH says nothing about spins.
I used to think the TriPacer was just ugly. It's still ugly, but it's an airplane that makes a lot of sense. Carries more than a 172, goes faster, takes off shorter and climbs better. Piper replaced it with the Cherokee because Cessna had the modern all-metal 172 that made the Tripe look dowdy. Another case of marketing trumping performance. Form over function. If I bought one I'd buy one that needed recover and I'd make a Pacer out of it, since only taildraggers are real airplanes, and I'd STC the pilot's side door into it, too.
Dan