Index: /branches/eam_branches/ipp-20211108/ippconfig/recipes/ppStack.config
===================================================================
--- /branches/eam_branches/ipp-20211108/ippconfig/recipes/ppStack.config	(revision 41938)
+++ /branches/eam_branches/ipp-20211108/ippconfig/recipes/ppStack.config	(revision 41939)
@@ -229,7 +229,8 @@
 END
 
-
-
-
+STACK_UNIONS_DR3 METADATA
+  COMBINE.PERCENT BOOL  TRUE     # Use a single percentile clipping?
+  SKIP.MISSING.INPUTS BOOL FALSE          # If some input warp images are missing, make the stack anyway
+END
 
 TEST1 METADATA
Index: /branches/eam_branches/ipp-20211108/ippconfig/recipes/reductionClasses.mdc
===================================================================
--- /branches/eam_branches/ipp-20211108/ippconfig/recipes/reductionClasses.mdc	(revision 41938)
+++ /branches/eam_branches/ipp-20211108/ippconfig/recipes/reductionClasses.mdc	(revision 41939)
@@ -2062,2 +2062,26 @@
         PSVIDEOPHOT                 STR     PSVIDEOPHOT
 END
+
+# UNIONS DR3 reduction class
+UNIONS_DR3  METADATA
+    CHIP_PPIMAGE                STR     CHIP
+    CHIP_PSPHOT                 STR     CHIP
+    WARP_PSWARP                 STR     WARP
+    STACK_PPSTACK               STR     STACK_UNIONS_DR3
+    STACK_PPSUB                 STR     STACK
+    STACK_PSPHOT                STR     STACK
+    DIFF_PPSUB	                STR	DIFF
+    DIFF_PSPHOT	                STR	DIFF
+    JPEG_BIN1                   STR     PPIMAGE_J1
+    JPEG_BIN2                   STR     PPIMAGE_J2
+    FAKEPHOT                    STR     FAKEPHOT
+    ADDSTAR                     STR     ADDSTAR
+    PSASTRO                     STR     DEFAULT_RECIPE
+    STACKPHOT_PSPHOT            STR     STACKPHOT
+    STACKPHOT_PPSUB             STR     STACKPHOT
+    STACKPHOT_PPSTACK           STR     STACKPHOT
+    STACKPHOT_SINGLE_PSPHOT     STR     STACKPHOT_SINGLE
+    BACKGROUND_PPBACKGROUND     STR     BACKGROUND
+    BACKGROUND_PSWARP           STR     BACKGROUND
+    PSVIDEOPHOT                 STR     PSVIDEOPHOT
+END