Noticed potential for tweaks whilst looking at the code, proposed patch against trunk to follow.
Attaching proposed patch against trunk.
Commit 1712087 from Christine Poerschke in branch 'dev/trunk'
[ https://svn.apache.org/r1712087 ]
SOLR-8218: DistributedUpdateProcessor (initialCapacity) tweaks
Commit 1712123 from Christine Poerschke in branch 'dev/branches/branch_5x'
[ https://svn.apache.org/r1712123 ]
SOLR-8218: DistributedUpdateProcessor (initialCapacity) tweaks (merge in revision 1712087 from trunk)