It now seems the capacity of the Gaelic Grounds in Limerick is a lot less than the 50,000 quoted.
"Munster Council officials, who are overseeing preparations for the clash, last night revealed that the stadium will have a capacity of close to 44,500. There will be reserved seating in the stand and that accounts for about 21,000 seats."
http://www.irishexaminer.com/sport/gaa/football/gaa-chiefs-anticipate-44500-sell-out-for-semi-final-replay-283593.html
"Munster Council officials, who are overseeing preparations for the clash, last night revealed that the stadium will have a capacity of close to 44,500. There will be reserved seating in the stand and that accounts for about 21,000 seats."
http://www.irishexaminer.com/sport/gaa/football/gaa-chiefs-anticipate-44500-sell-out-for-semi-final-replay-283593.html