hi Giles, and welcome!
I think to make the eraser working properly, you need to toggle
off the paper, not to "invert" it.
anyway, if you toggle off the paper, set the eraser (tool,size and power) as you wish,
and use the top-eraser of your pen, tvpa will record this tool, (with its settings
and paper's connection),
and each time you will re-use it, (drawing with the top of the pen), you will use the same tool (eraser + paper=off).
otherwise, you can use Custom Panel buttons,
- edit your "pencil" tool and add this command line (
type Script Command) :
- edit your "eraser" tool and add the command line :
(see pict.)
of course, you can also assign [Tools: Toggle Paper] to a shortcut, but imo, you shouldn't need it.
my 2 cents.