Hello Christina,
welcome to MEPD.
You can stick a coverstripe in the middle—you have to, to maintain the look. Sand the filled area cleanly and paint over it, and it'll be fine. This problem isn't unknown, and several members resort to this measure.
Another option is the thigh kit from RWA; he built larger molds specifically for this purpose.
You don't necessarily have to build up the edge; in the film, the thighs and shins were also slightly (subtly) cut out at the back to increase mobility. I would just cut out a slight curve: