There might be something genetic about it, but with the exception of my father who ran, hiked, and lifted weights until a few months before he died, everyone on both sides of my family are considerably heavier (more body fat) people than me (and even dad was 175-180 pounds most of his adult life). Like you said, maybe my metabolism is able to respond, but my activity level and nutrition certainly plays a part in that as well.Remco is a structural challenge. He's got a broad upper body that will only shed so much muscle without being injury compromised. Looking at most GT guys they look like their skeletal system was somehow replaced with child-width bones. They also break like glass when they hit the pavement. You clearly have the gift of metabolism that will modulate like that.
I'm really unimportant to my point that I think that RE CAN be at a 'good' GT weight if he really wants to.