Indices.cache.filter.size

I tried this :

curl -X PUT "localhost:9200/_cluster/settings?flat_settings=true&pretty" -H 'Content-Type: application/json' -d'{ "transient" : {"indices.queries.cache.size" : "20%"}}'

Getting this

{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_argument_exception",
        "reason" : "transient setting [indices.queries.cache.size], not dynamically updateable"
      }
    ],
    "type" : "illegal_argument_exception",
    "reason" : "transient setting [indices.queries.cache.size], not dynamically updateable"
  },
  "status" 
}

For a POC I needed to set the node query cache to 20% is this possible? or any alternatives are there? Basically I only want 20% of documents in cache not more than that.
Thanks.