diff --git a/src/preamble.tex b/src/preamble.tex
index 22139a2..00ae47e 100644
--- a/src/preamble.tex
+++ b/src/preamble.tex
@@ -42,10 +42,16 @@
 % emptied the log of underfull-box warnings, which looked like a win and was only the
 % goalposts moving. Do not raise it again without measuring (tools: work/rag.py).
 \setlength{\RaggedRightRightskip}{0pt plus 2em}
-% Lever 3: the default \parfillskip of 0pt plus 1fil accepts a last line of any length.
-% A finite fill makes TeX score a very short last line as badness and rearrange to
-% avoid one.
-\setlength{\RaggedRightParfillskip}{0pt plus 0.75\textwidth}
+% \parfillskip stays at ragged2e's default (0pt plus 1fil: a last line may be any
+% length). A finite fill was tried twice on 2026-09-14 and is not worth it. Badness is
+% 100(G/X)^3 for a gap G against stretch X and \tolerance=4000 accepts up to G ~ 3.4X,
+% with \rightskip adding its own 24pt — so on this 430pt measure any X at or above
+% 0.25\textwidth prescribes a threshold longer than the measure and can never fire
+% (0.75\textwidth was tried first and changed nothing at all). The only values in range
+% are 0.15 and 0.10\textwidth, and at 0.15 the cost lands on the interior lines: last
+% lines improve (p90 gap 319 -> 267pt) but paragraph-internal median rag goes 22.8 ->
+% 35.7pt, lines more than 3em short 29.4% -> 48.0%, and underfull boxes 123 -> 1902.
+% There are far more interior lines than final ones. Measured with work/rag.py.
 % The first line indents 1.6em; set here so \RaggedRight applies it rather than
 % relying on the direct \parindent assignment further down to repair it afterwards.
 \setlength{\RaggedRightParindent}{1.6em}