I had either the same or a very similar undersuit for my first outing with my Mark IV. I talk about it a bit in my build thread, I really like that it gives a "busy" look without needing to actually have anything underneath. I've since switched to a black undersuit (padded shirt) because I felt that the bright undersuit clashed a bit with my metallic blue armor, but I still think it's a great option for an undersuit, especially for the darker armor sets.
Also, I fully appreciate the Henry Cavill Fist Reload™ in the video. 10/10, no notes.