RE: What is the height of a snake of certain length?
In general, for most terrestrial snakes, I'd say they will "stand up" between 1/3rd - 1/2 of their body length, sometimes more. There is a great deal of variance in this between species.
I actually spent the weekend at a symposium a few weeks back on arboreal snakes that had a speaker, Dr Harvey Lillywhite, PhD., currently a professor of biology at the University of Florida. He has done extensive research on the physiological and behavioral ecology of amphibians and reptiles. His topic at the symposium was on the physiological adaptations of snakes, arboreal species in particular. It was a fascinating talk, comparing arboreal species, terrestrial species, and aquatic species (sea snakes), and how different they all are. Arboreal and semi arboreal species of snakes have adapted different circulatory systems that enable them to spend more time in a vertical position than most terrestrial snakes, to the extent of being able to cantilever over 75% of their body anchored to a branch.
They also have adaptations in their lungs based on the area they live, the different stresses of gravity and outside pressure.