SPARQL query to get capacity of event venues from Wikidata

Question

I am trying to query Wikidata to find out the capacities of all event venues in specific geographic regions (US urban centers). They have this service for querying: Wikidata Query Service

The answer in the related question below gave this query as an example for getting the capacities of arenas:

SELECT ?arena ?arenaLabel ?maximum_capacity WHERE {

  SERVICE wikibase:label { bd:serviceParam wikibase:language " 
   [AUTO_LANGUAGE],en". }

  ?arena wdt:P31 wd:Q641226.
  OPTIONAL { ?arena wdt:P1083 ?maximum_capacity. }
}

I tried to modify it a bit to get the capacities of event venues, not just arenas, but I don't get any results:

SELECT ?venue ?maximum_capacity WHERE {

  SERVICE wikibase:label { bd:serviceParam wikibase:language " 
   [AUTO_LANGUAGE],en". }

  ?venue wdt:P31 wd:Q7463935.

  OPTIONAL { ?venue wdt:P1083 ?maximum_capacity. }
}

I think the issue partly is that wd:Q7463935 says 'Category' so maybe 'wdt:P31' = 'is instance of' is not the correct way to phrase this.

Any ideas are much appreciated.

Related Question: Capacity/attendance information for US event venues