diff --git a/bdsg/include/bdsg/overlays/overlay_helper.hpp b/bdsg/include/bdsg/overlays/overlay_helper.hpp
index 8485bfa5..caeec671 100644
--- a/bdsg/include/bdsg/overlays/overlay_helper.hpp
+++ b/bdsg/include/bdsg/overlays/overlay_helper.hpp
@@ -66,10 +66,11 @@ template<typename T, typename U, typename V>
 class OverlayHelper {
 public:
     // Handle non-const base graph
-    T* apply(V* input_graph) {
+    template <typename ...Params>
+    T* apply(V* input_graph, Params&&... params) {
         auto mutable_overlaid = dynamic_cast<T*>(input_graph);
         if (mutable_overlaid == nullptr) {
-            overlay = make_unique<U>(input_graph);
+            overlay = make_unique<U>(input_graph, std::forward<Params>(params)...);
             mutable_overlaid = dynamic_cast<T*>(overlay.get());
             assert(mutable_overlaid != nullptr);
         }
@@ -78,10 +79,11 @@ class OverlayHelper {
     }
 
     // Handle const base graph
-    const T* apply(const V* input_graph) {
+    template <typename ...Params>
+    const T* apply(const V* input_graph, Params&&... params) {
         overlaid = dynamic_cast<const T*>(input_graph);
         if (overlaid == nullptr) {
-            overlay = make_unique<U>(input_graph);
+            overlay = make_unique<U>(input_graph, std::forward<Params>(params)...);
             overlaid = dynamic_cast<T*>(overlay.get());
             assert(overlaid != nullptr);
         }
@@ -100,6 +102,7 @@ class OverlayHelper {
 /// Implementation of overlay helper functionality for when multiple overlays need to be stacked.
 // There must be a way to generalize with variadic templates
 // (I had trouble chaining the output of the nested overlays together and getting the types right when trying)
+// TODO: Add support for passing overlay constructor arguments through.
 template<typename T1, typename U1, typename V1, typename T2, typename U2, typename V2>
 class PairOverlayHelper {
 public:
diff --git a/bdsg/include/bdsg/overlays/reference_path_overlay.hpp b/bdsg/include/bdsg/overlays/reference_path_overlay.hpp
index 1164e59c..a073c616 100644
--- a/bdsg/include/bdsg/overlays/reference_path_overlay.hpp
+++ b/bdsg/include/bdsg/overlays/reference_path_overlay.hpp
@@ -9,6 +9,7 @@
 #define BDSG_REFERENCE_PATH_OVERLAY_HPP_INCLUDED
 
 #include <unordered_map>
+#include <unordered_set>
 
 #include <handlegraph/path_position_handle_graph.hpp>
 #include <sdsl/bit_vectors.hpp>
@@ -30,7 +31,9 @@ class ReferencePathOverlay : public PathPositionHandleGraph {
         
 public:
     
-    ReferencePathOverlay(const PathHandleGraph* graph);
+    /// Create a ReferencePathOverlay. For paths with names in
+    /// extra_path_names, index them as if they were reference paths.
+    ReferencePathOverlay(const PathHandleGraph* graph, const std::unordered_set<std::string>& extra_path_names = {});
     ReferencePathOverlay() = default;
     ~ReferencePathOverlay() = default;
     
diff --git a/bdsg/src/reference_path_overlay.cpp b/bdsg/src/reference_path_overlay.cpp
index 8c69da41..f4ba79fd 100644
--- a/bdsg/src/reference_path_overlay.cpp
+++ b/bdsg/src/reference_path_overlay.cpp
@@ -6,25 +6,52 @@
 #include <omp.h>
 
 #include <handlegraph/util.hpp>
+#include <handlegraph/types.hpp>
 
 namespace bdsg {
 
 using namespace std;
 using namespace handlegraph;
 
-ReferencePathOverlay::ReferencePathOverlay(const PathHandleGraph* graph) : graph(graph) {
+ReferencePathOverlay::ReferencePathOverlay(const PathHandleGraph* graph, const std::unordered_set<std::string>& extra_path_names) : graph(graph) {
     
-    // init the base hash table and gather path handles
-    uint64_t max_path_handle = 0;
+    // Get step counts for all paths we want to process, once.
+    std::unordered_map<path_handle_t, size_t> cached_step_counts;
+    graph->for_each_path_matching({PathSense::REFERENCE, PathSense::GENERIC}, {}, {}, [&](const path_handle_t& path) {
+        // Find and measure all the reference and generic paths.
+        // TODO: Kick out generic paths?
+        cached_step_counts[path] = graph->get_step_count(path);
+    });
+    for (auto& path_name : extra_path_names) {
+        if (graph->has_path(path_name)) {
+            // The graph actually has this path.
+            path_handle_t path = graph->get_path_handle(path_name);
+            auto found = cached_step_counts.find(path);
+            if (found == cached_step_counts.end()) {
+                // And it's not already reference sense.
+                // Count steps and remember it
+                cached_step_counts.emplace_hint(found, path, graph->get_step_count(path));
+            }
+        }
+    }
+
+    // Now use the cache as a source of truth and make a vector of the paths. 
     std::vector<path_handle_t> path_handles;
-    graph->for_each_path_handle([&](const path_handle_t& path) {
+    // We also track the numerically max path handle
+    uint64_t max_path_handle = 0;
+    for (auto& handle_and_length : cached_step_counts) {
+        const path_handle_t& path = handle_and_length.first;
         path_handles.push_back(path);
+        
+        // Each of the paths needs a PathRecord
         reference_paths.insert(pair<path_handle_t, PathRecord>(path, PathRecord()));
+        // And needs to be maxed into the max handles.
         max_path_handle = std::max<uint64_t>(max_path_handle, handlegraph::as_integer(path));
-    });
+    }
+
     // sort in descending order by length to limit parallel scheduling makespan
     std::sort(path_handles.begin(), path_handles.end(), [&](path_handle_t a, path_handle_t b) {
-        return graph->get_step_count(a) > graph->get_step_count(b);
+        return cached_step_counts.at(a) > cached_step_counts.at(b);
     });
     
     std::vector<std::atomic<size_t>> num_steps(graph->max_node_id() + 1);
@@ -35,7 +62,7 @@ ReferencePathOverlay::ReferencePathOverlay(const PathHandleGraph* graph) : graph
         auto& path_record = reference_paths.at(path);
         
         // init the step vectors
-        size_t path_size = graph->get_step_count(path);
+        size_t path_size = cached_step_counts.at(path);
         path_record.steps.resize(path_size);
         
         // record the steps and the path length