And another heard from on the rack size: it's too small. The 3U Rackbrute is better used to expand the Minibrute by adding a few things that it doesn't have. But to do a proper build, you'd need to start with the 6U version...and I'd even think that THAT was a bit small unless you're good at using alternatives to the full-sized modules.
These 3U builds simply DO NOT WORK unless you're designing something very specific that can fit into that small a space. Otherwise, you'll tend to run into that space limitation over and over. Yes, you see these on YouTube all the time. But those are either done by very experienced modular users OR they're unworkable pieces of crap cobbled together by someone who needs to stay the HELL off of YT and stop misleading people.