Everything you ever wanted to say about "Zebra luvin", but didn't because you thought everyone would take the mickey! Plus general topics for discussion including everything from what you feed them to your personal experiences.
I have a little bit sticking out here and there and it doesn't seem to bother them. I guess as long as it's not taking up too much space on the inside it would be OK.
As long as it's not bulging out and creating crevices where the eggs/newborns could be stuck, then I don't see a problem with it.
Remove the excess silicone when it's newly applied, and if you get some sticking out here and there it doesn't matter - for the fish that is.
Personally I'm quite annoyed with the silicon that shows around the caves in my terrace tank, but I try not to worry too much about it and pray for algae - the right kind mind you!