Excellent Marcel !
I suspected you had made the same mistake I did when I first looked at this.
So, now the period (order) of rnd is established. That makes many things easier. In particular, I am working on inverse-rnd by way of Nth-iterate by way of b-functions. In the process I'll also find inverse-takeoff.
b-functions are slower to evaluate, but easier to compose in this case (only 32 binary terms in any iterate and each equation will fit into 32 bits because of the xors).
I'll show the results here soon.
Happy Forthing, Marcel.
Sincerely,
James Gere