Not sure if this helps Houghy but I recently purchased a few D series items (dove tail ring set; universal plate) from Anthony Davoli (ADM Accessories) and I am of the understanding that they are somewhat lighter than the equivalent original Losmandy products - eg. ADM's side-by-side saddle, etc. Beautifully made, very reasonable prices and excellent communication. The items purchased seem rock solid but there may be others who feel differently.
You could flick Anthony an e-mail and he will generally respond promptly with the weight of any item (perhaps even a comparative weight)
http://www.admaccessories.com/FORMgallery2.htm