obviously this depends on bone density also etc.
a very simple method would be e.g
divide weight by height in inches.
eg 300lbs at 6'2 (74") =4.05lbs per inch
to work out what a 5'6 bbuilder would weigh to be at the same size is simple.
5'6"= 66 inches
66x4.05= 267lbs
im guessing this is extremely flawed