Remote fill lid leaking

Hello
I have one of your basic master cylinders with the remote fill lid. My problem is I can not stop the lid from leaking. It is not tight enough to stop the fluid from leaking out when the plastic reservoir is filled. The clamps that came in the package with the remote fill lid are too short and will not go no matter what I do. The clamps that came with the master to hold on the regular lid are not holding the remote fill tight enough. I have tried bending the clamp a little to make them tighter but still no luck.
Any suggestions?

Check the master for any casting dips or bumps in the casting; Being aluminum the lid will not flex like a stock one so the surface needs to be perfect. Also, the bails must be super tight. Use the ones that came with the kit.