There are some things which don't yet update to reflect changes to tpt.el, they are: ...., and can_move (changes to tpt.el.properties and tpt.el.weight don't affect which elements displace which other elements).
can_move also controls whether particles can occupy the same space, i.e. whether something is transparent to neutrons. This will be fixed in the next version.
How do I change "can_move" in the Lua script? Is can_move one of the tpt.el.elem.properties things I can change? If so, which number code represents the can_move constant?
It's a 2D array (with dimensions PT_NUM x PT_NUM), and at the moment it can't be directly changed using Lua. The values in it can be indirectly affected by changing tpt.el.properties and tpt.el.weight, but it won't update when those are changed using Lua until the next update is released.