I would like to sister a joist 16 ft long, but make it go the entire span as the original joist (both ends of the original joist rest on a supporting wall, and I want the new sister to rest on the supporting wall on both ends as well.) Something tells me that even if I angle the new joist at an angle and flip it horizontal, I'll be able to squeeze it into the space, BUT will have trouble trying to flip it back upright. This is a ceiling of a 2 story house, so there is plywood sheets above the joist that I cannot easily remove.