diff --git a/tests/infrastructure/epc_client/test_sap_accuracy_corpus.py b/tests/infrastructure/epc_client/test_sap_accuracy_corpus.py
index 2f454359..079f4e01 100644
--- a/tests/infrastructure/epc_client/test_sap_accuracy_corpus.py
+++ b/tests/infrastructure/epc_client/test_sap_accuracy_corpus.py
@@ -163,6 +163,20 @@ _CORPUS = Path(
 # Took within-0.5 70.3% -> 71.6% (MAE 0.833 -> 0.822); fixed the 2 stone-U
 # unit tests; worksheet-validated (Elmhurst age-B sandstone 400 mm → 1.90).
 #
+# STONE MECHANISM CORRECTED (RdSAP 10 Tables 6-7 footnote a + §3.5 Table 3):
+# the commit above (034d4b7c) got the right numbers for two cases but the
+# wrong mechanism — it dropped the 1.7 cap for ALL age bands and gated on
+# `wall_insulation_type is not None`. Per Tables 6-10: bands A-D = uncapped
+# §5.6 formula, band E = min(formula, 1.7) (Scotland sandstone 1.5); the cap
+# is age-E ONLY. The insulation-state gate is not a spec rule (it sent
+# age-A-D "insulation Unknown" stone to the flat 1.7 table). Unknown
+# thickness now feeds the §3.5 Table-3 default thickness (stone A-D 500 mm,
+# E 450; Scotland +200/+100) into the formula — Elmhurst defaults an England
+# age-B granite as-built unknown-thickness wall to 500 mm → 1.87 (sandstone
+# 1.68), NOT a flat 1.7. Also added the missing Scotland band-J 0.30 override
+# (Table 7) for all 7 as-built wall types. MAE 0.822 -> 0.819, PE 3.7 -> 3.6;
+# within-0.5 and CO2 unchanged. Unit-pinned in test_rdsap_uvalues.
+#
 # SAP RATING FLOOR (SAP 10.2 §13 / RdSAP 10 §13): the rating is floored at 1
 # ("if the result is less than 1, the rating is 1"). `calculate_sap_from_inputs`
 # now applies that floor to the CONTINUOUS score too (was integer-only), so a
@@ -170,9 +184,9 @@ _CORPUS = Path(
 # (cert 422000111926, lodged at the floor of 1, was computing -11.3): within-0.5
 # 70.2% -> 70.3%, MAE 0.845 -> 0.833.
 _MIN_WITHIN_HALF_SAP = 0.71
-_MAX_SAP_MAE = 0.83
+_MAX_SAP_MAE = 0.82
 _MAX_CO2_MAE_TONNES = 0.09      # t CO2 / yr vs co2_emissions_current
-_MAX_PE_PER_M2_MAE = 4.0        # kWh / m2 / yr vs energy_consumption_current
+_MAX_PE_PER_M2_MAE = 3.7        # kWh / m2 / yr vs energy_consumption_current
 
 
 def _load_corpus() -> list[dict[str, Any]]: