For this kind of problems (and wanting to use Kisslicer, because I tweaked it the best of all my used slicers) I use the
on the style tab. For this particular object a value of (minus) -0.05mm resulted in complete letters.
I can't imagine that the object being 0.05mm x 2 = 0.1 mm bigger in XY is a problem, but when: scale it in Kisslicer to compensate: as it is about 20mm, scaling it with 19.9/20=0.995x (or 20/20.1? same result) before slicing it with the -0.05mm offset.
It's probably a quick and dirty method, but it works with Kisslicer.
I agree with you: for this kind of objects (specially thin walled) Slice3r doing the best job. Yes it's still around and has some nice features other slicers don't have. And that's a good thing, as there will probably not be a slicer which can 'do-it-all" in the direct future. Keep all tools at hand...
I always use 0.05mm oversampling / 1mm crowning for this delicate print paths and always keping my pathwidths to 0.4mm, being the nozzle size.
Bart