Sims 2 Castaways: How build Mansion Bungalow on third island?

Hi, the game will not let me build the Maniosn Bungalow in the Volcano Overlook area (although I have all the materials and it is highlighted as available). It's a great location and one of the few with enough room for it. When I went to the second island in the Plains area ... it allowed me it to build there, but I don't want it there. Any thoughts? Any other suggested locations to build that big bungalow? I don't want to waste the materials on anything smaller. Thanks!