FPRUtility is throwing out of memory error while merging fpr files

I am trying to merge two fpr files using FPRUtility but it is throwing out of memory error. Ample physical memory is available in the high-capcity machine with 256 GB RAM and 48 cpu cores.

[releng@subgm23 17.2]$ free -g

             total       used       free     shared    buffers     cached

Mem:           251          2        249          0          0          0

-/ buffers/cache:          1        250

Swap:            7          0          7

I have set the JVM size in fortify.properties file as:

com.fortify.model.ExecMemorySetting=80G

[releng@subgm23 17.2]$ FPRUtility -merge -project Fortify-occs-version17.1-3rdParty-scan.fpr -source Fortify-occs17.2-3rdParty-scan.fpr -f Fortify-occs17.2main-3rdParty-scan.fpr

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

        at java.util.Arrays.copyOfRange(Arrays.java:3664)

        at java.lang.StringBuffer.toString(StringBuffer.java:671)

        at java.io.BufferedReader.readLine(BufferedReader.java:327)

        at java.io.BufferedReader.readLine(BufferedReader.java:389)

        at com.fortify.ui.model.util.fpr.LocalAuditFileLoader.isOldFormatAuditXml(LocalAuditFileLoader.java:487)

        at com.fortify.ui.model.util.fpr.LocalAuditFileLoader.isOldFormat(LocalAuditFileLoader.java:461)

        at com.fortify.ui.model.util.fpr.LocalAuditFileLoader.doMerge(LocalAuditFileLoader.java:54)

        at com.fortify.ui.model.ProjectLoader.loadAuditInfo(ProjectLoader.java:298)

        at com.fortify.ui.model.ProjectLoader.loadAdditionalFPRInfo(ProjectLoader.java:241)

        at com.fortify.ui.model.ProjectLoader.updateProject(ProjectLoader.java:465)

        at com.fortify.ui.model.ProjectLoader.loadProject(ProjectLoader.java:203)

        at com.fortify.ui.model.ProjectLoader.loadProject(ProjectLoader.java:185)

        at com.fortify.ui.model.util.integration.IntegrationStubFactory$2.loadProjectWithProgress(IntegrationStubFactory.java:90)

        at com.fortify.ui.model.util.integration.IntegrationUtil.loadProjectWithProgress(IntegrationUtil.java:150)

        at com.fortify.ui.model.util.integration.IntegrationUtil.loadProjectWithProgress(IntegrationUtil.java:116)

        at com.fortify.ui.model.util.fpr.FPRCommandlineInterface.performMerge(FPRCommandlineInterface.java:747)

        at com.fortify.ui.model.util.fpr.FPRCommandlineInterface.main(FPRCommandlineInterface.java:232)

[releng@subgm23 17.2]$

Any idea what I am doing wrong? Thanks much in advance.