I read somewhere that TDC is where the timing chain is at its loosest. Doesn't seem to make sense to me, as aren't all the sprockets located in fixed locations? It's not as if the chain sits on the cam lobes themselves which are eccentric.
Any way to ensure the chain hasn't slipped before firing up the engine? I guess for the really paranoid, would this work? Put a paint mark on the timing chain when you first find TDC, and then confirm it's still in the same position once the new tensioner is place, and the engine turned around a couple revolutions?
I finished the APE install on mine and so far haven't blown up the engine. But wasn't comfortable with the leap of faith of firing up the engine without some form of prelim double check.