Tadpole recumbent trikes are stabile for the same reason they are hard to get up from the seat ,
and a Porsche corners better than a pickup truck .. the Low center of Gravity..
High crown road ,( for drainage ), on a typical Upright trike, you may just have to lean towards the center of the road crown..
It would be a complicated and so a heavy thing, to have the whole thing perpendicular to the center of the earth
in spite of the road crown.
Maybe a gimbaled cup holder from a Boating store will have to Do.
http://i.ebayimg.com/00/s/MTYwMFgxNj...S6ELt/$_35.JPG