One of these costs a little more than 10% of that contraption and you don't need to cobble it together. Strong enough to lift a GSA off the ground.
Cut it down to make it easier to pack. It does not need to lift the bike completely vertical, just past the point of no return and you can take over from there.
It's called a ratcheting cargo bar. You can pick one up at most auto parts stores, harbor freight, home depot, lowes, e.t.c.
Stay away from the model by Highland, it's made cheaply.