QPR chief Executive Lee Hoos says the club are aiming for a capacity of 30,000 for their prospective new stadium.
The Hoops are currently looking towards the site of the Linford Christie Athletics stadium in White City for the new site, which is over three-times the size of the Loftus Road site.
Responding to a question about the previously discussed 40,000 seater stadium at the Supporters Consultation Commitee, Hoos said: "No, a 40,000 capacity is too much.
"It should be remembered that the original proposition at Old Oak was very different (to the plans in White City).
"We need to consider the Championship model and in the Championship it would be very difficult to sell 40,000 tickets.
Looking at what Leicester and Southampton have done, 30,000 would seem about right."
Speaking about the prospect of any other sites becoming available, Chief Operating Officer Mark Donnelly said: "At the moment there aren’t any other sites in Hammersmith and Fulham.
"We have looked at many sites overthe last few years but they have been used for other developments.
"Linford Christie looks to be the only option that would keep us in the Borough."