Recently my pool light popped out of it's housing assembly and floated to the top.

I got a new retainer ring, new gasket and (eventually) a new screw.

I took off the old gasket and retainer ring, let everything dry out, and replaced them.
I had my husband help me with tightening the metal clamp that holds everything together and thought I had it tight enough.

To test for leaks, I've had the light fixture floating while waiting on the new screw to arrive.
Turns out I did not have everything tight enough, as the fixture was full of water, that started to SLOWLY leak out of the gasket area (I did look for drips near cord entry, didn't see any) when I pulled the light out today.

Several google searches have netted me no help on how tight that darn metal ring clamp should be. How far apart should the two ends be?

Also, is it possible I had the gasket in wrong? I had it so that the smooth side was facing the plastic retainer ring and the bump side was facing the metal light fixture.

Any advice/input is greatly appreciated!