I learned a trick from somewhere on the internet to let the snake crawl into a tube to measure its length. I have this tupperware-type container that holds uncooked spaghetti and I let him crawl in there and he straightened out quite good enough to get a good measurement.

Great looking ball python you got there! I'm too new to snakes to know anything about recessives and all these types of morphs. So, I tend to assign a value to the snake by the way it "looks".