In my old compaq rack, it is quite wide and deep, so it's not a problem, I can mount my PDU extension bars to the side where they do not block anything.
Since your rack is a bit more limited due to the acoustic dampening, you will have to mount it to your rack post.
Because your rack is not very deep, I hope you have a few servers that don't extend all the way to the back, put those together and mount this PDU vertically behind them? (make sure to allow access to cables and good airflow)
I think I saw a picture
@Patrick posted where he ran into a few problems with one of his racks not being deep enough too.
I forgot what it was but he tried to mount something that hit a PDU he mounted to his back right rack post.