According to http://docs.splunk.com/Documentation/Splunk/latest/admin/indexesconf you can define the following stanzas, so Yes you should be able to shutdown Splunk, move the files and make the change.
tstatsHomePath =
* Required.
* Location where datamodel acceleration TSIDX data for this index should be
stored
* MUST be defined in terms of a volume definition (see volume section below)
* Must restart splunkd after changing this parameter; index reload will not
suffice.
* CAUTION: Path must be writable.
* Defaults to volume:_splunk_summaries/$_index_name/datamodel_summary,
where $_index_name is runtime-expanded to the name of the index
summaryHomePath =
* An absolute path where transparent summarization results for data in this
index should be stored. Must be different for each index and may be on any
disk drive.
* May contain a volume reference (see volume section below).
* Volume reference must be used if data retention based on data size is
desired.
* If not specified, Splunk will use a directory 'summary' in the same
location as homePath
* For example, if homePath is "/opt/splunk/var/lib/splunk/index1/db",
then summaryHomePath would be "/opt/splunk/var/lib/splunk/index1/summary".
* CAUTION: Path must be writable.
* Must restart splunkd after changing this parameter; index reload will not
suffice.
* Defaults to unset.
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