I had a Pi Bar for a short time and now have a Shadow bar. I got the Pi Bar when I was planning on building a 36er with a 25.4mm post but I ended up using a KH frame and 27.2mm post so wasn’t able to use it. I did ride with the Pi Bar on my 24" for a while to try it out and really liked using it.
The Pi Bar would be a good fit on a 29er. It’s a good length and has good adjustability. The Shadow set gives more options in how it can be setup but is probably overkill on a 29" wheel. It’s also more than twice as much money.