Hi Michael,
since you can enter +2.5 on Z (whence you had 5); would it be possible to incorporate on any given dimension f(d); where f is a function (+, -, *, /) and d is the dimensional value of X, Y, or, Z? This would allow to generate some geometries with proportions; for instance X could be 2*Z. The difficulty for at least a novice user would be to avoid creating a circular relationship.

Cheers,

- Diego -