diff --git a/qpms/qpms_c.pyx b/qpms/qpms_c.pyx
index c2437ad..d659a8b 100644
--- a/qpms/qpms_c.pyx
+++ b/qpms/qpms_c.pyx
@@ -696,7 +696,7 @@ cdef class ScatteringSystem:
                 self.s, iri, 0)
         return target_np
 
-    def pack_matrix(self, fullmatrix, iri):
+    def pack_matrix(self, fullmatrix, iri, version='normal'):
         """Converts (projects) a matrix into an irrep subspace.
 
         Parameters
@@ -728,10 +728,14 @@ cdef class ScatteringSystem:
         cdef np.ndarray[np.complex_t, ndim=2] target_np = np.empty(
                 (rlen, rlen), dtype=complex, order='C')
         cdef cdouble[:,::1] target_view = target_np
-        qpms_scatsys_irrep_pack_matrix(&target_view[0][0], &fullmatrix_view[0][0],
+        if version == 'stupid':
+            qpms_scatsys_irrep_pack_matrix_stupid(&target_view[0][0], &fullmatrix_view[0][0],
+                self.s, iri)
+        else:
+            qpms_scatsys_irrep_pack_matrix(&target_view[0][0], &fullmatrix_view[0][0],
                 self.s, iri)
         return target_np
-    def unpack_matrix(self, packedmatrix, iri):
+    def unpack_matrix(self, packedmatrix, iri, version='normal'):
         """Unpacks an "irrep-packed" excitation coefficient vector to full coordinates.
 
         Parameters
@@ -764,7 +768,11 @@ cdef class ScatteringSystem:
         cdef np.ndarray[np.complex_t, ndim=2] target_np = np.empty(
                 (flen, flen), dtype=complex, order='C')
         cdef cdouble[:,::1] target_view = target_np
-        qpms_scatsys_irrep_unpack_matrix(&target_view[0][0], &packedmatrix_view[0][0],
+        if version == 'stupid':
+            qpms_scatsys_irrep_unpack_matrix_stupid(&target_view[0][0], &packedmatrix_view[0][0],
+                self.s, iri, 0)
+        else:
+            qpms_scatsys_irrep_unpack_matrix(&target_view[0][0], &packedmatrix_view[0][0],
                 self.s, iri, 0)
         return target_np
 
@@ -816,6 +824,16 @@ cdef class ScatteringSystem:
                     qpms_scatsys_periodic_build_translation_matrix_full(&target_view[0][0], self.s, wavenumber, &blochvector_c, eta)
         return target
 
+    def irrep_transform_matrix(self, qpms_iri_t iri):
+        self.check_s()
+        cdef size_t rlen = self.saecv_sizes[iri]
+        cdef size_t fullen = self.fecv_size
+        cdef np.ndarray[np.complex_t, ndim=2] target = np.empty(
+                (rlen, fullen), dtype=complex, order='C')
+        cdef cdouble[:,::1] target_view = target
+        qpms_scatsys_irrep_transform_matrix(&target_view[0][0], self.s, iri)
+        return target
+
     def translation_matrix_packed(self, cdouble wavenumber, qpms_iri_t iri, J = QPMS_HANKEL_PLUS):
         self.check_s()
         cdef size_t rlen = self.saecv_sizes[iri]
diff --git a/qpms/qpms_cdefs.pxd b/qpms/qpms_cdefs.pxd
index 7394265..42e6423 100644
--- a/qpms/qpms_cdefs.pxd
+++ b/qpms/qpms_cdefs.pxd
@@ -645,6 +645,11 @@ cdef extern from "scatsystem.h":
             cdouble omega, const qpms_tolerance_spec_t *tol)
     qpms_scatsys_at_omega_t *qpms_scatsys_at_omega(const qpms_scatsys_t *ss, cdouble omega)
     void qpms_scatsys_at_omega_free(qpms_scatsys_at_omega_t *ssw)
+    cdouble *qpms_scatsys_irrep_transform_matrix(cdouble *target, const qpms_scatsys_t *ss, qpms_iri_t iri)
+    cdouble *qpms_scatsys_irrep_pack_matrix_stupid(cdouble *target_packed,
+            const cdouble *orig_full, const qpms_scatsys_t *ss, qpms_iri_t iri)
+    cdouble *qpms_scatsys_irrep_unpack_matrix_stupid(cdouble *target_full, 
+            const cdouble *orig_packed, const qpms_scatsys_t *ss, qpms_iri_t iri, bint add)
     cdouble *qpms_scatsys_irrep_pack_matrix(cdouble *target_packed,
             const cdouble *orig_full, const qpms_scatsys_t *ss, qpms_iri_t iri)
     cdouble *qpms_scatsys_irrep_unpack_matrix(cdouble *target_full,