You've got a good base to work on there, in fact you've got more than a base, you're already a decent size. For your height though I'd be happier being 15st. Though i'm over 15st I still feel I need a bit more - around 100kg would be my max, though a solid 98kg would be ideal. Problem with being over 6' tall is that long limbs make it harder to "look" big....