As HH said. In my Fraim I have the 300PS on the top shelf of the brawn and the 300 HU on the bottom of the brain so that the burndies don’t touch the floor. Same for the 552 - the head unit on the top of the brain and the 552 PS on the bottom of the brawn.
Related question on Burndy. Having a side by side rack there’s high traffic of burndy and signal cables behind the rack. Is there a general “rule” in burndy not touching other burndy and signal cables not touching burndy etc. Separating boxes is great but it also adds a cables nest which is pretty challenging to arrange properly… Powerlines are not close to either burndy or signal cables and the SNAIC on 552 is approx 1-2cm away not touching the burndy all the way.