But most of that weight is water. You can only put fat back on so fast (3500kcal / lb roughly).
The answer to that conundrum, as you say, RC, is to control the carbs on the way back up.
The rebound after a natural show, in terms of muscle mass, may actually be larger than after having done a show on gear, because of the dramatic differences in hormone levels.
Compare the hormonal differences between a guy on a gram of stuff / week during his prep and after. Major change would be insulin (minus that used during his prep.), and maybe IGF-1, unless he's doing this too.... Test. and other androgens will increase IGF-1 output, so the change ma be little here.
A natty may have reduced test., certainly insulin, and IGF-1 levels during his (or her) prep. and these hormones will increase dramatically when the "re-feeding" occurs.
The key to not creating a sloppy water-logged fat mess is to have some degree of control after a show and "ride the rebound."
During the few weeks after the show, anabolism is maximized. The basic idea would be to maximize nutrition to support that, but not overdo it with calories that are not needed (but still enjoy life, shit - its needed at that point.) LOTS of good quality food...
-Randy