diff --git a/src/cactus/cactus_progressive_config.xml b/src/cactus/cactus_progressive_config.xml
index 427eae7ab..f9eb9b349 100644
--- a/src/cactus/cactus_progressive_config.xml
+++ b/src/cactus/cactus_progressive_config.xml
@@ -111,6 +111,7 @@
 		   dechunkBatchSize="1000"
 		   pickIngroupPrimaryAlignmentsSeparatelyToOutgroups="1"
 		   slurmChunkScale="3"
+		   bigGenomeChunkScale="2"
 		   >
 
 		<!-- The following are parametrised to produce the same results as the default settings,
@@ -550,6 +551,8 @@
 			seq_size_1000000000="128000000000"
 			seq_size_4000000000="256000000000"
 			seq_size_10000000000="512000000000"
+			seq_size_15000000000="999000000000"
+			seq_size_20000000000="1990000000000"
 	 	/>
 	</consolidated>
 	<consolidated2></consolidated2>
diff --git a/src/cactus/preprocessor/cactus_preprocessor.py b/src/cactus/preprocessor/cactus_preprocessor.py
index a1d3253db..b4cfa18a3 100644
--- a/src/cactus/preprocessor/cactus_preprocessor.py
+++ b/src/cactus/preprocessor/cactus_preprocessor.py
@@ -90,7 +90,8 @@ class CheckUniqueHeaders(RoundedJob):
     """
     def __init__(self, prepOptions, inChunkID):
         disk = 2*inChunkID.size
-        RoundedJob.__init__(self, memory=prepOptions.memory, cores=prepOptions.cpu, disk=disk,
+        memory = max(prepOptions.memory, inChunkID.size)
+        RoundedJob.__init__(self, memory=memory, cores=prepOptions.cpu, disk=disk,
                      preemptable=True)
         self.prepOptions = prepOptions
         self.inChunkID = inChunkID
diff --git a/src/cactus/preprocessor/cutHeaders.py b/src/cactus/preprocessor/cutHeaders.py
index 1b857d7d2..6e2934b10 100644
--- a/src/cactus/preprocessor/cutHeaders.py
+++ b/src/cactus/preprocessor/cutHeaders.py
@@ -17,6 +17,7 @@
 class CutHeadersJob(RoundedJob):
     def __init__(self, fastaID, cutBefore, cutBeforeOcc, cutAfter):
         disk = 2*(fastaID.size)
+        memory = fastaID.size
         RoundedJob.__init__(self, disk=disk, preemptable=True)
         self.fastaID = fastaID
         self.cutBefore = cutBefore