Also, you make use of E000/1/2. As you point out, the chance of these
being used is small, but not non-zero.

I would suggest using Private-use characters from plane 17 instead
(and somewhere in the middle of the plane, not at the start of the
block). This would reduce the chance of a collision further, I think.

Of course, it would still not be zero. In particular, trying to run
the transformation against itself is guaranteed to find a collision :-)
-- 
Colin Adams
Preston Lancashire