This is a good exercise for big guys to practice manipulating their bodyweight. Start with 15-second holds.
Considering that 90% of the athletes capable of performing a true iron cross are 5'3", 135-pound gymnasts with obscene strength-to-weight ratios, most people think they can't do it. But that changes if you simply adjust the lever arm.
In the video, I've used my sleeves and placed them high up on the arms for support (for bigger frames, this is definitely needed). From that point on, the goal is just to free-hang while driving the shoulder blades down as best as possible and squeezing the glutes and core.
This is more difficult than it looks. Don't let your arms rest against the bars of the squat cage, though, as that would make things much easier.
The lats and abs go crazy in this variation while simultaneously salvaging the shoulder and elbow joints from way too much stress, way too soon.
To make it harder, just move the sleeves a couple of inches farther away from your body. Don't be a fool and add a weight belt with three 45-pound plates attached to it.