There is a side by side LW5 being built in Spain i think (or in Europe somewhere) and i cleared the pictures i had of it off my computer. It has a 48" wide cabing and a fuel tank/bench seat made from fiberglass. The challenge with the side by side design will be ballance when flying solo, especially with fuel weight ballance so ballast will need to carried and/or a trim device on the mast for side trim. I feel a side by side is very doable for the LW design, the Phenix is a SXS and it looks to fly very well.
James, like you i dont care for the "GEEBEE" look of the LW5 tandem two place as there is no definition for the vertical fin, that is why i made mine a single place with a very defined transition from the turtle deck to the vertical fin, that and i was not going to solo from the back seat!
Tim