I have a 4.2, and someone else below in the reviews has a Tres 3.1 - and they have the same problem. The PSU is too big to fit horizontally between the pedalboard's rails - on Rockboard's own pedalboard! You'd think when they sell accessories they'd be designed to work well together, but this is just as half thought out as their mod patch bays that don't screw in properly because the Warwick team painted the screwholes and got paint into the threads. So if you want to use this with a Rockboard, you're going to be turning it 90 degrees which then means ... wait for it ... the separate plate accessory they sell no longer protects all of the PSU. No joined up thinking at Rockboard at all.
All that said, it's a beast for power output. I'm driving an Eventide H90, Hotone Tuner Press, EHX Mel 9, EHX Key 9, Boss VE-20, Boss WL-60 (Hot garbage, don't buy ...) and a Markbass Vintage Pre Pedal. And I have loads of outputs free to add more if I need them.