for my sprint diamond, I had to do it in mutiple steps:
1) Disable TF3D.
2) Install the Sprint2Flip cab
3) Soft Reset
4) re-enable TF3D and make sure you've got the standard Flip clock with the black numbers on the creme/white background.
5) disable TF3D again
6) With the Sprint2Flip clock still installed, install the cab file for the final flip clock style you want (like the Holy cab I installed for the white shaded numbers on the clear background).
7) Soft reset.
re-enable TF3D again.
Should be good to go.