Yes I like that Bowie Squatch as well .... and like HD I tend to just leave the dimples near the ricasso .... if you try and get to them with the belt sander there is a risk of removing the primary grind line on the blade and dovetailing the blade straight into the ricasso .... you can however drill the tube fastener on one side and use a hammer and punch to remove the grips and as HD says then use the platen for the flat sections .... I find gluing on a strip of leather to the platen makes for a much more uniform and comfortable ability to press the knife/belt onto the platen ...
If I did remove the tubes and grips I think I might be tempted to buy some "hex bolts" from a knife maker supplier and try those so that the grips could be removed if you wanted to do so for cleaning the knife .... I believe you can get bolts such as these to work as I have seen others do it .... and if you were so inclined you could replace the tubes and flare them using sawn off screw heads and pressing them in to flare the tube using a large vice ....