I discovered these American recumbent tricycles selling on eBay (£276 new in Germany + £8 delivery!)
The size (length and width) looks nearly ideal for the C5 and its adjustable with rear suspension I think. Maybe this could be a replacement chassis and since it has better rear wheel assembly, it might make for an interesting upgrade mod if someone wanted to do a rear hub drive C5 and have a better seat?
Not sure about the steering though!!
MOBO Triton Recumbent Tricycle



eBay Seller page:
http://tinyurl.com/zjmzeld