I was just thinking the same Toby.For a regular Motoro she's beautiful,just goes to show you don't need to spend lots of cash to own a nice Stingray.
I would say 6 pups,she's huge to say she's only just over half way through gestation......are you sure you have your dates right,she looks almost ready to drop.
Good luck!
pups from this have about a 3 in 4 chance of looking motoro and a 1 in 4 chance of looking like a leo but....motoro is dominant so probably all looking like motoros
look up Linnaean genetics punnet ( mendel) square for better info.
here is a link, work it out for yourself http://anthro.palomar.edu/mendel/mendel_2.htm