The Silque comes with the 28, but I opted to have the 32 put on. I don't think it cost any more. Yes, the Trek site is very difficult to use. My suggestion is to go to an LBS and have the person look in the "big book" from Trek to find what you want. I had written down the geometry of the older WSD Madone I had on my tour in Portugal. That was the predecessor to the Silque. By doing that, the LBS owner could look in the book and find the newer Silque version. It took some work, but what you want is not difficult to get.