^ i think it would still be an overkill to switch the venue of the semis and the finals of the volleyball games this season to the Araneta Coliseum. like what you mentioned, only a handful of sections of Araneta will be filled up since UAAP volleyball has yet to achieve the same kind of following that UAAP basketball has.
the relatively expensive ticket prices at the Big Dome might also turn off the mostly non-alumni supporters of UAAP volleyball teams (remember that the current prices of tickets at The Arena are roughly half of the prices of tickets at the Araneta Coliseum).
UAAP volleyball, unlike UAAP basketball, has a rather "personal" touch because fans at The Arena are close to the action on court. sa Araneta kasi, may kalayuan ang court sa die-hard supporters na madalas ay nasa Upper A at Upper B sections.
for now, UAAP volleyball, an event that yet to assert itself popularity-wise, will be better off staying at The Arena, its "home" for several years now. if the main concern of the host is accommodating the "large number of people" who will come to the big games, ULTRA, with its maximum seating capacity of 10,000, is the best "big" venue for the games, for now.