the lower the initital size the bigger the chance it will be a large S class
thus gas/desert have low land and a higher chance of being huge when they are S class
and btw 10X is NOT max for an S class
2X-10X are the most probal
with some gas over 1k planets can be aprox 200X larger
think of a 10K+ u large with an S bonus of 200X or more :)