diff --git a/brush-strokes/src/cusps/bench/Main.hs b/brush-strokes/src/cusps/bench/Main.hs
index 17eb870..06a3a34 100644
--- a/brush-strokes/src/cusps/bench/Main.hs
+++ b/brush-strokes/src/cusps/bench/Main.hs
@@ -92,14 +92,15 @@ benchGroups :: [ ( String, NE.NonEmpty TestCase ) ]
 benchGroups =
   [ ( "ellipse"
     , NE.fromList
-      [ ellipseTestCase opts ("ε=" ++ show narrowAbs)
+      [ ellipseTestCase opts ("ε_bis=" ++ show ε_bis ++ if doBox1 then "box(1)" else "")
           ( 0, 1 ) pi
           ( defaultStartBoxes [ 0 .. 3 ] )
-      | narrowAbs <- [ 5e-2, 1e-6 ]
+      | ε_bis <- [ 1e-6, 5e-6, 1e-5, 5e-5, 1e-4, 5e-4, 1e-4, 5e-4, 1e-3, 5e-3, 1e-2, 5e-2, 0.1, 0.2, 0.3 ]
+      , doBox1 <- [ False, True ]
       , let opts =
               RootIsolationOptions
                 { rootIsolationAlgorithms =
-                    defaultRootIsolationAlgorithms minWidth narrowAbs
+                    defaultRootIsolationAlgorithms minWidth ε_bis doBox1
                 }
       ]
     )
diff --git a/brush-strokes/src/lib/Math/Root/Isolation.hs b/brush-strokes/src/lib/Math/Root/Isolation.hs
index 2decabc..e568a39 100644
--- a/brush-strokes/src/lib/Math/Root/Isolation.hs
+++ b/brush-strokes/src/lib/Math/Root/Isolation.hs
@@ -102,7 +102,7 @@ newtype RootIsolationOptions n d
 defaultRootIsolationOptions :: BoxCt n d => RootIsolationOptions n d
 defaultRootIsolationOptions =
   RootIsolationOptions
-    { rootIsolationAlgorithms = defaultRootIsolationAlgorithms minWidth ε_eq
+    { rootIsolationAlgorithms = defaultRootIsolationAlgorithms minWidth ε_eq True
     }
   where
     minWidth = 1e-5
@@ -114,10 +114,11 @@ defaultRootIsolationAlgorithms
   .  BoxCt n d
   => Double -- ^ minimum width of boxes (don't bisect further)
   -> Double -- ^ threshold for progress
+  -> Bool -- ^ do box1
   -> BoxHistory n
   -> Box n
   -> Either String ( NE.NonEmpty ( RootIsolationAlgorithmWithOptions n d ) )
-defaultRootIsolationAlgorithms minWidth ε_eq history box =
+defaultRootIsolationAlgorithms minWidth ε_eq doBox1 history box =
   case history of
     lastRoundBoxes : _
       -- If, in the last round of strategies, we didn't try bisection...
@@ -133,7 +134,8 @@ defaultRootIsolationAlgorithms minWidth ε_eq history box =
     -- Otherwise, do a normal round.
     -- Currently: we try an interval Gauss–Seidel step followed by box(1)-consistency.
     _ -> Right $ AlgoWithOptions @GaussSeidel _gsOptions
-            NE.:| [ AlgoWithOptions @Box1 _box1Options | not verySmall ]
+            NE.:| [ AlgoWithOptions @Box1 _box1Options
+                  | doBox1 && not verySmall ]
 
   where
     verySmall = and $ ( \ cd -> width cd <= minWidth ) <$> coordinates box