To make Versor usable with a very small number of keys (for example, a mouthswitch), it is possible to reverse the motion of Versor's “forward” and “back” commands (of all kinds, both dimensions and both meta-dimensions (ways of choosing dimensions). This is available through the command versor-reverse. If reversing is used, it appears in the mode line as an arrow at the appropriate end of the dimension indication.
This is an extreme solution, for extreme problems. It's unlikely to be useful if you can use Versor in other ways.