Sverrir,
nope, the sponge is just there to contain the area, then glue is poured in to fill the void. The horns are then inserted into the glue (and the excess wiped off )
Actually, it was something I learned from a good friend here, John, he is an "old rat" when it comes to building, and I'm just a n00b (but I'm good at copying what others do )

Hans,
you know deep in your heart that you need the P200SX, don't resists [>:]