Casting hollow clear resin horns?

Hey guys,

OK, the thing is, one of the next parts of my head will be a pair of horns, which I want to make out of clear resin (this being so I can stick LEDs inside them, and leave exposed spots in the paint so I get light spots down the length of the horns when they are switched on). But I have a feeling that the best thing would be to make them hollow, so I can get the LEDs in there, and also to reduce weight as much as possible.

My plan is to make the sculpt, and then the silicone mold - and then cut the mold in half, and cast each side separately and stick them together. Is this an acceptable way of going about what I'm trying to do? Or is there a better way? (I'm going for highly realistic horns, apart from the light spots)

I was just wondering, what is the best way to go about making a more or less hollow horn 'half' from the resin? I assumed it can't be slush cast like polyurethane resin. Has anyone had any experience of doing something like this? I would greatly appreciate advice from people who know more about this than me :P

Thank you guys :)