I bought one extra mountain bracket to my TB Duo 34 pedalboard, because I have a pretty big powersupply, and I really want it to sit tight underneath.
But I guess I will get more if I wanna expand my board with more pedals. As you can mount them underneath then switch them on/off with a looper instead. As long as you don't wanna tweak your pedals that often.
Was a bit tricky to install it though, seems the pedalboard expanded some millimeters after I installed all my pedals, But got it on eventually.