I ran across this while checking out the grip board forum.  I seems the monster bell virus is catching on with others.  This is of course very cool.  Adam Glass who is pretty well known on some of the grip forums and over on Dragon Door made a 50 kg bell from an 8kg shell.  It is interesting to see how he did this. In the video below. It is a different approach than I have used.  I like it though and I am a little surprised the bucket didn't melt.  The sand apparently did a great job of insulating the system.  His results were similar to mine using just lead.  He got it up to 50 kg.  Mine would end up at about 52kg.  Much of this difference probably has to do with the quality of the lead.  You can see all the crud at the top of the bell at the end.  It is better to use lead that has been fluxed a few times.  That's all I'm going to say.  We can't give away all our secrets.  I wish I had a torch like these guys.