I'd wager no lower than 25% or higher than 35% From a purely mechanical perspective having a bit of mass in certain events is advantageous (anything that's deadlifty/pressy) but also a draw back from a CV perspective (dragging/carrying) stuff. Pudzinowski and The Mountain have visible abs when they diet down and while they'll certainly have thicker cores than the average that's something you only start to see sub 15% BF (technically more sub 10% if we're talking complete popping out of the trunk musculature).