I guess I've never driven it sideways on a really steep hill. Don't have many of those where I live, but its center of gravity is pretty low I think because there's lots of heavy metal below 24 inches or so. I think the cab makes it look tall, too.
I'd guess the basic machine was ready to test-drive in about 4-6 months. I never kept track, but it became sort of an obsession for me (I'd sometimes even get up early in the morning and go out to the shop to work on it).
I've sometimes wondered if for folks like me who like to invent, engineer, and build stuff with their hands are somewhat like poets, writers, and composers who just have a "drive" to do their things: it just sort of comes out.