no need for those high reps, treat the like any other muscle you want to grow....
heres one
4x10-15 hanging leg raises
4x10-15 cable cruches
**next time you train abs**
hangin leg raises
decline crunches
** ***
mix it up, i will always use hanging leg raises because i feel they are superior to any other lower abdominmal developement. also because there are a lot of people who lack lower abs