[azapa]

I just built one this weekend, 2Kg. Tips:
- try to use a double layer of innertube, a thinner inner, then the outer (my fist attempt was a single, and it split)
- to get 2Kg into a well fitting neckweight you will need to pack the shot well, there is only one way: compressed air. with the tubes closed at one end, 1/2 fill, inflate with the compressor (i guess a bike pump would do) and wiggle and massage the lead down. Repeat two or three fill/inflate/wiggle sessions.
- make it small enough to not fall over you chin when your head is upside down, but loose enough not to pinch your throat with a wetsuit on.
- use the finest lead shot you can find
- use superglue to seal the ends
- use electrical tape to finish the ends