Teardrops n Tiny Travel Trailers

Hi
Has anyone designed a teardrop with footwell to allow a trifold mattress to also serve as a sofa, like the Vistibule model?
I have started a few design options but would appreciate anyone's experience in this regard both in mattress as well as integration issues.
I think I will do a mockup for sure to make sure the proportions feel right. I was thinking about 6.5-7 inch footwell depth.
thanks

Here is a fairly recent build that was done with a sofa bed. http://tnttt.com/viewtopic.php?f=50&t=66429&start=0 Do a search up top for sofa bed