I won't be receiving my new C'dale until December 15th so I am not able to answer your question. Our bike dealer rented us a Burley (medium) which is very similar in size to the C'dale L/S and the one we ordered. The dealer was able to compare measurements and fitted my wife and I prior to the rental and it was a great experience. Both of the bike shop owners own tandems, so their experience was a lot of help. They were able to select the best size for us and make any needed changes (such as stem size, seat post, etc.) when we pick it up. I already know that the stem will have to be changed, as the stock is a little short for me.
If your dealer was able to get you the correct frame size for you (which seems to be the largest they make), your dealer should be able to fit you properly with the measurements shown on the C'dale website geometry and specification information (may be some minor changes will be needed, but you probably won't know that until you get your bike).
Hopefully this helps. Good Luck!!