fuzzynaval - never wear anything at night. Ever. Too many stories of things going wrong regardless of what anyone might say.
pulacalului - the tension on the elastic should be about 2 pounds according to the instructions I received. I have not measured it myself, but I think mine is about that. Starting with lower tension helps get you used to how to wear it and the feeling.
The silicone sleeve is more of a cub than a sleeve. You roll it up and then roll it over your head which suction-cups it into place. Be careful to get your whole head in though or it will get sore. I start mine by centering the cap just a little higher than my pee hole. Otherwise, part of my glans tend to stick out and I have to take it off and try again.