I also do it when I pull the engines out, I trust it to hold the engine and trans. Look at this way, I would rather have 4 bolts with the forces pulling straight up on all 4 then have 2 bolts pulling up sideways on them. As long as the threads are good in the manifold. I also throw a chain with a couple of bolts as a safety measure, I too think about the weight on the Aluminum.