Well now your observations are very true.
Regular belts are not great to work mammoth tooth. They will have a tendency to tear and chip. Silicon carbide belts from True grit are what you want and believe it or not i suggest getting only a couple which are 120 and a fine 40 I belive it is. The 120 will handle sizing down and shaping and work the tooth very nicely. If you plan to do lots more get a 60 grit as well in the silicon carbide of course. To begin with you will need to get some backing on the scales after you have got them flat. Even before that take and coat the scales first one side then the other with the thin crazy glue. I get enough on to use a hobby paint brush and spread it around well. Maybe two coats on the bottom side. I use the thin micarta from Alpha knife supply. I also recommend placing another piece of the same on the top side as well using that crazy glue again. Lots of care must be taken when drilling holes. It's best to use carbide bits turning at the fastest speed your drill press will do but with very light down pressure and lots of cutting fluid. Cobalt will also work. I did try regular new ones for a while with only limited success. The piece of thin micarta you glued on to the up side of the scales is to help prevent the drill bit poping through and tearing out the top of the hole. You can make very pretty handles with this stuff but I personally would not use it on a knife to see use. Oh yes, don't be surprized if some where along you have one or both crack on you . Just place the pieces together and you guessed it, use more crazy glue. I hope this helps. I have found it to be the most difficult of the more common natural materials to work with. Still, I think I'm using more as time goes by. Frank