diff --git a/src/libslic3r/Fill/FillBase.cpp b/src/libslic3r/Fill/FillBase.cpp
index 4a56cddaef..8ae8a6d4a7 100644
--- a/src/libslic3r/Fill/FillBase.cpp
+++ b/src/libslic3r/Fill/FillBase.cpp
@@ -171,16 +171,11 @@ void Fill::fill_surface_extrusion(const Surface* surface, const FillParams& para
                 params.extrusion_role,
                 flow_mm3_per_mm, float(flow_width), params.flow.height());
         }
-
-        if (is_flow_calib) {
+        if (!params.can_reverse || is_flow_calib) {
             for (size_t i = idx; i < eec->entities.size(); i++)
-                eec->entities[i]->reverse();
-        } else {
-            if (!params.can_reverse) {
-                for (size_t i = idx; i < eec->entities.size(); i++)
-                    eec->entities[i]->set_reverse();
-            }
+                eec->entities[i]->set_reverse();
         }
+
         // Orca: run gap fill
         this->_create_gap_fill(surface, params, eec);
     }
diff --git a/src/libslic3r/Fill/FillPlanePath.cpp b/src/libslic3r/Fill/FillPlanePath.cpp
index b867ee83a0..2167e3704b 100644
--- a/src/libslic3r/Fill/FillPlanePath.cpp
+++ b/src/libslic3r/Fill/FillPlanePath.cpp
@@ -120,8 +120,33 @@ void FillPlanePath::_fill_surface_single(
     if (polyline.size() >= 2) {
         Polylines polylines = intersection_pl(polyline, expolygon);
         Polylines chained;
-        if (params.dont_connect() || params.density > 0.5 || polylines.size() <= 1)
-            chained = chain_polylines(std::move(polylines));
+        if (params.dont_connect() || params.density > 0.5 || polylines.size() <= 1) {
+            // ORCA: special flag for flow rate calibration
+            auto is_flow_calib = params.extrusion_role == erTopSolidInfill &&
+                                 this->print_object_config->has("calib_flowrate_topinfill_special_order") &&
+                                 this->print_object_config->option("calib_flowrate_topinfill_special_order")->getBool() &&
+                                 dynamic_cast<FillArchimedeanChords*>(this);
+            if (is_flow_calib) {
+                // We want the spiral part to be printed inside-out
+                // Find the center spiral line first, by looking for the longest one
+                auto it = std::max_element(polylines.begin(), polylines.end(), [](const Polyline& a, const Polyline& b) { return a.length() < b.length(); });
+                Polyline center_spiral = std::move(*it);
+
+                // Ensure the spiral is printed from inside to out
+                if (center_spiral.first_point().squaredNorm() > center_spiral.last_point().squaredNorm()) {
+                    center_spiral.reverse();
+                }
+
+                // Chain the other polylines
+                polylines.erase(it);
+                chained = chain_polylines(std::move(polylines));
+
+                // Then add the center spiral back
+                chained.push_back(std::move(center_spiral));
+            } else {
+                chained = chain_polylines(std::move(polylines));
+            }
+        }
         else
             connect_infill(std::move(polylines), expolygon, chained, this->spacing, params);
         // paths must be repositioned and rotated back