I've created a couple of examples, I guess it will aid diagnosing:
Basically, I remove the standard 8mm scale (and I think that for very small translations/rotations even the 4mm could be removed). I also increased the smoothing at each level.
In this case, it is pretty much the same as before, but now I add the option 'setoption paramsubset 1 0 0 0 0 0 0 1 1 1 1 1 1' in order to only optimize scalings and skews.
My problem is that this language is a bit difficult to understand. Basically I'm testing by chance.
I think that, when one inserts the optimise command, the 'amount' of transformation is controlled by the last part (something of this kind: 'rel 4') but I'm not sure of the implications of this parameter.
e.g. optimise 7 UA:1-4 1.0 0.0 0.0 0.0 0.0 0.0 0.0 rel 4
I'm also unsure about the first schedule, around the end, when it tries again the identity transform. I'm not sure this is taken into account (these copy U UA commands are quite obscure to me, sorry).
Thank you so much
Best wishes,
Oscar