diff --git a/Makefile b/Makefile
index 551125c9b..3805837cc 100644
--- a/Makefile
+++ b/Makefile
@@ -41,8 +41,9 @@ dsk: asm
 # precompute FX and DFX indexes and merged data files containing multiple
 # graphic effects in a single file (loaded at runtime by LoadIndexedFile())
 #
-	bin/buildfx.sh "res/FX.CONF" "build/FX.IDX" "build/FX.ALL" "build/FX.INDEXED" >>build/log
-	bin/buildfx.sh "res/DFX.CONF" "build/DFX.IDX" "build/DFX.ALL" "build/FX.INDEXED" >>build/log
+	rm -f "build/FX.ALL"
+	bin/buildfx.sh -p "res/FX.CONF" "build/FX.IDX" "build/FX.ALL" "build/FX.INDEXED" >>build/log
+	bin/buildfx.sh -p "res/DFX.CONF" "build/DFX.IDX" "build/FX.ALL" "build/FX.INDEXED" >>build/log
 #
 # substitute special characters in help text and other pages that will be
 # drawn with DrawPage()
@@ -57,18 +58,16 @@ dsk: asm
 # mini-attract mode configuration, and prelaunch files
 #
 	bin/buildhelp.sh "res/GAMES.CONF" "build/GAMEHELP.IDX" "build/GAMEHELP.ALL" "build/GAMEHELP" >>build/log
-	rm -f build/SSDIR.CONF && touch build/SSDIR.CONF >>build/log
-	for f in res/SS/*; do \
+	(for f in res/SS/*; do \
 	    bin/buildokvs.sh "$$f" "build/SS/$$(basename $$f)"; \
-	    echo "$$(basename $$f)" >> build/SSDIR.CONF; \
-	done
-	bin/buildfx.sh "build/SSDIR.CONF" "build/SLIDESHOW.IDX" "build/SLIDESHOW.ALL" "build/SS" >>build/log
-	rm -f build/ATTRACTDIR.CONF && touch build/ATTRACTDIR.CONF >>build/log
-	for f in res/ATTRACT/*; do \
+	    echo "$$(basename $$f)"; \
+	done) > build/SSDIR.CONF
+	bin/buildfx.sh -p "build/SSDIR.CONF" "build/SLIDESHOW.IDX" "build/SLIDESHOW.ALL" "build/SS" >>build/log
+	(for f in res/ATTRACT/*; do \
 	    bin/buildokvs.sh "$$f" "build/ATTRACT/$$(basename $$f)"; \
-	    echo "$$(basename $$f)" >> build/ATTRACTDIR.CONF; \
-        done
-	bin/buildfx.sh "build/ATTRACTDIR.CONF" "build/MINIATTRACT.IDX" "build/MINIATTRACT.ALL" "build/ATTRACT" >>build/log
+	    echo "$$(basename $$f)"; \
+	done) > build/ATTRACTDIR.CONF
+	bin/buildfx.sh -p "build/ATTRACTDIR.CONF" "build/MINIATTRACT.IDX" "build/MINIATTRACT.ALL" "build/ATTRACT" >>build/log
 	bin/buildhelp.sh "res/GAMES.CONF" "build/PRELAUNCH.IDX" "build/PRELAUNCH.ALL" "build/PRELAUNCH.INDEXED" >>build/log
 #
 # create _FileInformation.txt files for subdirectories
@@ -95,9 +94,8 @@ dsk: asm
 		build/HELPTEXT \
 		build/ATTRACT.IDX \
 		build/FX.IDX \
-		build/FX.ALL \
 		build/DFX.IDX \
-		build/DFX.ALL \
+		build/FX.ALL \
 		build/GAMEHELP.IDX \
 		build/GAMEHELP.ALL \
 		build/SLIDESHOW.IDX \
diff --git a/bin/buildfx.sh b/bin/buildfx.sh
index 2c4b5b6e6..8cc3561c9 100755
--- a/bin/buildfx.sh
+++ b/bin/buildfx.sh
@@ -2,18 +2,31 @@
 
 # run from project root directory
 
+# flags
+# -p  pad merged file size to next block size (default off)
+
 # parameters
 # 1 - input filename of text file containing list of effects (probably FX.CONF or DFX.CONF)
 # 2 - output filename for index file
 # 3 - output filename for merged-effects file
 # 4 - input directory of (previously assembled) effects files
 
-# create or truncate merged-effects file
-:>| "$3"
+pad=false
+while getopts ":p:" opt; do
+      case $opt in
+          p) pad=true
+             shift
+             ;;
+      esac
+done
+
+# create merged data file if it doesn't exist, but do not truncate it
+# (we may call this script more than once with the same data file)
+touch "$3"
 
 # make temp file with list of effect names
 records=$(mktemp)
-grep -v "^$" < "$1" | grep -v "^#" | grep -v "^\[" > "$records"
+awk '!/^$|^#|^\[/ { print }' < "$1" > "$records"
 
 # make temp assembly source file that represents the binary OKVS data structure
 source=$(mktemp)
@@ -31,10 +44,14 @@ source=$(mktemp)
      # This padding does not get added to the file; it is just an
      # optimization to avoid a partial copy on the last block read.
      size=$(wc -c < "$4/$key")
-     if [ $(($offset / 512)) -eq $((($offset + $size) / 512)) ]; then
-         echo "$size"
+     if [ "$pad" = true ]; then
+         if [ $(($offset / 512)) -eq $((($offset + $size) / 512)) ]; then
+             echo "$size"
+         else
+             echo "$(((($offset + $size + 511) & -512) - $offset))"
+         fi
      else
-         echo "$(((($offset + $size + 511) & -512) - $offset))"
+         echo "$size"
      fi
      cat "$4/$key" >> "$3"             # add effect code into merged-effects file
                                        # (all effects were previously assembled)