I tighten up the bolts until it hits bottom and then just a little snug past that. It's very obvious when they are all the way down.
Sean
You DO have to be careful when tightening thse bolts, not only because of threading into AL, but also some pretty flimsy cast 'posts'...
When I tighten these type bolts, I simply hold the socket & ratchet head in between my fingers, then twist my wrist, so I'm not applying any leverage to the 'arm' of the ratchet...Have been doing that with threads in AL for years, in cars & bikes, I get the bolt 'snugged up' nicely, get a pretty consistent 'torque', & have never stripped a thread that way yet...
(where's that pesky piece of wood...???...Knock, Knock!!!...LOL)