I have a custom made chinrest (from chinrests.com) on my primary instrument, but I also have an electric violin and a violin I use outdoors. I simply measured the custom one and got the 40mm version of this chinrest as the closest match. I love it.
If you have a long neck, you should probably have a raised chinrest!
I don't use a shoulder pad - I prefer to feel the violin on my collar bone and gently secure it with my chin. In order to do that comfortably, the distance between the bottom of my violin and the top of my chinrest has to match pretty closely the gap between my collar bone and chin.
This is on my electric instrument (again, 40mm) - thus the stickers :)