If its the ariel, silicone the TOP side not the bottom...i.e. on the mating part of the plastic ariel base with the threaded aprt and the locating pin....this will ensure it doesnt leak around there and rust the edges like if you did the under side.
The sunroof always leaks, and its generally just down to a persihed seal or one that has moss (yes moss) growing inbetween the shel and the seal...there is a little wire type seal bit which goes round under the seal which gets lifted by moss...clean it all up and place some vaselene around the seals and under. The water which comes through the light that comes from the sunroof is because the water leaking past the seals gets into the runenrs and collects in a box section space at the front, above the windy bit....you can jsut access it from the top when you wind the roof back.........clean this area.....i would have used a turkey baster....but couldnt find one, so i used a straw and my mouth...not nice.
