I don't know a whole lot about them, but what about a white lipped python? From what I understand Northerns top out around 7-8 feet and Southerns get closer to 10 feet. The Northerns appear to be at the top of your size preference, but after a very quick glance around the web they might be something you'd be interested in. Maybe check them out and do some homework?
Liaisis can be... interesting. Nippy. Flighty. I wouldn't recommend them as a first snake.
I would suggest a dwarf or central-American locality BCI that has passed the baby/juvi defensive phase.