Index: trunk/psModules/src/objects/pmSourceFitModel.c
===================================================================
--- trunk/psModules/src/objects/pmSourceFitModel.c	(revision 31153)
+++ trunk/psModules/src/objects/pmSourceFitModel.c	(revision 32347)
@@ -176,7 +176,9 @@
         break;
       case PM_SOURCE_FIT_EXT:
-        // EXT model fits all params (except sky)
-        nParams = params->n - 1;
+        // EXT model fits all shape params and Io (not Xo, Yo, sky)
+        nParams = params->n - 3;
         psVectorInit (constraint->paramMask, 0);
+        constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_XPOS] = 1;
+        constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_YPOS] = 1;
         constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_SKY] = 1;
         break;
@@ -193,11 +195,13 @@
 	break;
       case PM_SOURCE_FIT_NO_INDEX:
-        // PSF model only fits Io, index (PAR7) -- only Io for models with < 8 params
+        // PSF model only fits Io, Sxx, Sxy, Syy
 	psVectorInit (constraint->paramMask, 0);
+        constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_XPOS] = 1;
+        constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_YPOS] = 1;
 	constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_SKY] = 1;
         if (params->n == 7) {
-	    nParams = params->n - 1;
+	    nParams = params->n - 3;
 	} else {
-	    nParams = params->n - 2;
+	    nParams = params->n - 4;
 	    constraint->paramMask->data.PS_TYPE_VECTOR_MASK_DATA[PM_PAR_7] = 1;
 	}