diff --git a/pykat/optics/maps.py b/pykat/optics/maps.py
index 64d0aefdf329f4bc48a3d84fc273801babb65eab..8bdf6f90f64ba7b1dbd5e6c746c9091f76ff82d5 100644
--- a/pykat/optics/maps.py
+++ b/pykat/optics/maps.py
@@ -143,28 +143,30 @@ class surfacemap(object):
             raise BasePyKatException("Map type needs handling")
         
 
-    def generateROMWeights(self, isModeMatched=True, verbose=False, interpolate=False, tolerance = 1e-12, sigma = 1, sort=False, greedyfile=None):
+    def generateROMWeights(self, isModeMatched=True, verbose=False, interpolate=False, interpolate_N=None, tolerance = 1e-12, sigma = 1, sort=False, greedyfile=None):
         
         if interpolate:
             from scipy.interpolate import interp2d
             import numpy as np
 
             D = interp2d(self.x, self.y, self.data, fill_value=0)
-
+            if interpolate_N is None:
+                interpolate_N = (self.size[0], self.size[1])
+                
             # only want even number of data points spread equally
             # about the axes
-            if self.size[0] % 2 == 0:
-                Nx = self.size[0]
+            if interpolate_N[0] % 2 == 0:
+                Nx = interpolate_N[0]
             else:
-                Nx = self.size[0]-1
+                Nx = interpolate_N[0]-1
 
-            if self.size[1] % 2 == 0:
-                Ny = self.size[1]
+            if interpolate_N[1] % 2 == 0:
+                Ny = interpolate_N[1]
             else:
-                Ny = self.size[1]-1
+                Ny = interpolate_N[1]-1
             
-            nx = np.linspace(min(self.x), max(self.x), Nx) 
-            ny = np.linspace(min(self.y), max(self.y), Ny)
+            nx = np.linspace(min(self.x), max(self.x), interpolate_N[0]) 
+            ny = np.linspace(min(self.y), max(self.y), interpolate_N[1])
             
             data = D(nx-self.offset[0], ny-self.offset[0])
             
diff --git a/pykat/optics/romhom.py b/pykat/optics/romhom.py
index 7119fb4366866df19b2a4c4659bb2da89dc5f765..ac12c673509615a2431a4b85d0ed93b1aed50f9d 100644
--- a/pykat/optics/romhom.py
+++ b/pykat/optics/romhom.py
@@ -28,37 +28,48 @@ class ROMWeights:
         self.limits = limits
         
     def writeToFile(self, filename):
-        f = open(filename, 'w+')
+        """
+        Writes this map's ROM weights to a file
+        that can be used with Finesse. The filename
+        is appended with '.rom' internally.
+        """
+        f = open(filename + ".rom", 'w+')
         
-        f.write(repr(self.limits) + "\n")
+        f.write("zmin=%16.16e\n" % self.limits.zmin)
+        f.write("zmax=%16.16e\n" % self.limits.zmax)
+        f.write("w0min=%16.16e\n" % self.limits.w0min)
+        f.write("w0max=%16.16e\n" % self.limits.w0max)
+        f.write("maxorder=%i\n" % self.limits.max_order)
         
+        f.write("xnodes=%i\n" % len(self.EI["xm"].nodes))
+        
+        for v in self.EI["xm"].nodes.flatten():
+            f.write("%s\n" % repr(float(v)))
+        
+        f.write("ynodes=%i\n" % len(self.EI["ym"].nodes))
+        
+        for v in self.EI["ym"].nodes.flatten():
+            f.write("%s\n" % repr(float(v)))
+            
         f.write(repr(self.w_ij_Q1.shape) + "\n")
         
         for v in self.w_ij_Q1.flatten():
-            f.write("%s " % repr(complex(v))[1:-1])
-        
-        f.write("\n")
+            f.write("%s\n" % repr(complex(v))[1:-1])
         
         f.write(repr(self.w_ij_Q2.shape) + "\n")
         
         for v in self.w_ij_Q2.flatten():
-            f.write("%s " % repr(complex(v))[1:-1])
-        
-        f.write("\n")
+            f.write("%s\n" % repr(complex(v))[1:-1])
         
         f.write(repr(self.w_ij_Q3.shape) + "\n")
         
         for v in self.w_ij_Q3.flatten():
-            f.write("%s " % repr(complex(v))[1:-1])
-        
-        f.write("\n")
+            f.write("%s\n" % repr(complex(v))[1:-1])
         
         f.write(repr(self.w_ij_Q4.shape) + "\n")
         
         for v in self.w_ij_Q4.flatten():
-            f.write("%s " % repr(complex(v))[1:-1])
-        
-        f.write("\n")
+            f.write("%s\n" % repr(complex(v))[1:-1])
             
         f.close()