Those bulky rockboard cables on the back of his Boss unit are the flat MIDI rockboard cables. You can see he cut the rubber around the right one to fit, and I had to do the same to mine. With an exacto knife and a careful hand you can completely remove the rubber as it’s mosly for stress relief.
I went all out with the ones I had and also did a vertical slit and removed the entire jacket. Leaves just the metal sleeve & hard white plastic back. Believe it or not the white cap does an awesome job of keeping it all together. I’ve changed the board layout a bunch of times and they have never failed me!
Allows for some really tight midi patching, I’d say if you’re brave enough this is the most low profile configuration that’s not even on the market!
You can see how fat the OneControl looks on the bottom right of my Soleman compared to the decapitated Rockboard midi.
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Also- the gold 1/4” patch cables are the Rockboard patch cables. They are a bit longer but soooo flat.