Be careful! Make sure the transformer is a listed class II transformer - I know a lot of the WAC jobs do not carry a listing for "field installations". (You can tell by the reverse R and U together - this indicates that UL recognizes this product but it is to be used as a component of another product). If the wiring behind the walls is zip cord and connected to these lights the transformer has to be a LISTED class II to protect against fire and shock hazard. I have also seen the lighting you have indicated in the 120 volt varity - if it is, your customer may have a problem, and also a hazard. You can check the listing number at www.ul.com to see what the product is listed for.