http://gcaptain.com/cruise-ship-lengthening-balmoral-time-lapse-video/ [some footage that shows the the German Yard and the naval architects know what they're doing.

From Wikapedia:

"Reconstruction[edit]Fred. Olsen took delivery of the ship on 7 November 2007, renaming her after the Balmoral estate. The company initiated a major refit at the Blohm + Voss repair shipyard in Hamburg, Germany, before her inaugural cruise on 13 February 2008, to Florida—her base for Caribbean cruising. The work included the insertion of a 30 meter (99 ft) midsection, built in conjunction with Schichau Seebeckwerft in Bremerhaven, and floated into Hamburg at the end of October 2007.[7][8]

The reconstruction added a further 186 passenger and 53 crew cabins, making the ship currently the company's largest. It also introduced 60 new balconies, along with new and modified public areas, all designed to appeal particularly to the British cruise market.[7][9][10]"

From the Shipping Times:
"German shipyard to lengthen cruise ship for Fred Olsen
NORWEGIAN CROWN will take name of BALMORAL and enter UK cruise market in 2008

Fred. Olsen Cruise Lines has now entered into a contract with Blohm + Voss Repair GmbH, Hamburg for a lengthening of the NORWEGIAN CROWN by approximately 30 meters. The lengthening will increase the passenger capacity with about 35% and provide more cabins with balconies.

The cost of the total project which now includes the purchase of the cruise ship, the upgrade and the lengthening will amount to about USD 210 million.

The 1988-built NORWEGIAN CROWN is currently operating under a bareboat charter to NCL (Olsen purchased her last year) and is due for redelivery to Fred. Olsen Cruise Lines Pte. Ltd. early November 2007. Following completion of the lengthening and upgrading of the vessel in January 2008, the vessel will commence cruise operations for Fred.Olsen Cruise Lines as the BALMORAL

These investments, said the company, underline Fred.Olsen Cruise Line's ongoing commitment towards the UK cruise market, which has seen 20 years of continuous growth."

The welding was only the first part:

"Fred Olsen cancels Balmoral's first cruise
By Kelly Ranson | 28 January 2008 at 17.30 GMT
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Fred Olsen Cruise Lines has cancelled the inaugural cruise of its latest ship Balmoral, which was due to depart for the Canary Islands on January 30.

The ship, which was previously NCL’s Norwegian Crown, has just undergone an extensive refit, including lengthening the middle. A number of technical issues have arisen meaning further work must be undertaken before the ship can start its cruise programme.

The cruise line is compensating all passengers and the second planned cruise, due to depart Dover for the Caribbean on February 13, remains on schedule.

Fred Olsen managing director Mike Rodwell said: “Naturally, we are extremely disappointed that we had to take this difficult decision and have apologised to the customers affected by it.

“The complex lengthening and refurbishment work onboard has been ongoing since we took delivery of the ship in November 2007 and we were confident that the vessel would be ready for service in good time. However, a number of unforeseen technical issues have emerged in the past week and these have led to this unfortunate decision being taken”.