Wow........he is huge. I would think that he is almost full grown. If he was 30lbs @ 4 months and weigh 60lbs at mature weight then isnt that about average?
I don't think that will work for Gator. At 4 months he was around 28lbs (if I remember right) and at the vet today he weighed in at 51lbs and he is 8.5 months old.
51lbs at 8.5 years......he must have peaked at 55?