Related to what I posted immediately before you – the thinning pattern is irregular for fractional tilt_strengths. Immediate workaround is to work with tilt strengths of zero or one.
The key bit that I am contemplating stems from remarks in post 16 in the ABN thread. For ±N in the pink area for tilt_strengths<0.5, we obtain thickness indirectly from the green quadrilateral whose height has not entirely vanished. But that configuration still admits the segment P–Pp aligning with ±N at some other orientation, in particular orientations that approach tilt_angle+90° as tilt_strength approaches 0.5.
For tilt_strength > 0.5 ±T orientation dominates and the thin parts thicken, but only at one orientation, tilt_angle+90° and at tilt_strength = 1.0 ±N wholly coincides with ±T and the calligraphic effect is turned off.
Not clear to me yet the reconfiguration approach that needs to be worked out. A cuppa coffee or two, and a few relaxing meetings with assistant commissioners, and it might be clear to me.