I played around with the valve yesterday, my thoughts are that the secondary drain should be accepting enough water to semi-fill the pipe. Why? Anything less tends to crash down the length of the pipe, adding a very small amount of noise.
Also, definitely need to seal up the secondary inside the cap. I am thinking that I'll just use silicone. It should come out with some twisting if necessary, and since this is slip cap -> threaded adapter, no worries of it locking threads up.
I made a shelving unit for our pantry yesterday, so not a lot of progress. Hopefully some more updates by end of day today. Yay Labour day long weekend.