Finally got around to assessing the leftover timber in the backyard for whether it's usable for building the ramp.
It's, uh... not heartening. I have a feeling that I'll be lucky to get the four uprights that I need out of the three pieces. I might be lucky enough to get two frame pieces, but I doubt it somehow, with how bad the dry rot is in two of the pieces.
Which does make the entire project far more annoying, though I wasn't feeling confident about that timber being okay anyway.