I had been carrying a 12 foot telescoping ladder in the basement for 2 years, and I installed a ladder to get away from the need to carry a ladder in the basement. So installing a half ladder would not have accomplished what I wanted. As for the need to fold the ladder to access the engine bay, it is no problem at all. You just pull 2 pins and lift it up. It takes less than 5 seconds, and there is no way that I will carry a ladder in the basement to avoid a 5 second task. Especially when dealing with the ladder in the basement will take so much more time, and take up valuable storage area to a fulltimer like me. The only reason that I ever saw for a half ladder is to make the ladder less accessible to children because of liability, or criminals for security reasons.
When I installed the mounting screws, I definitely hit a reinforced area every time, even on the roof. I know this because the screws were so hard to turn all of the way down that I was afraid of breaking them off.
Gerald