As mentioned, it's pretty difficult to get TDC exactly unless you use a degree wheel, but it isn't really necessary either...[8D]

Just line up the trigger in the hub with the casting rib that is on the engine's left side as you look at it from the back. Normally I just tell people to use the side opposite the exhaust, but since you've got an RE, that doesn't work!

Now if you've got any kind of an eye for lining stuff up straight, this will get you well within acceptable limits and is the way everyone I know with a ZDZ does it. Works just fine.

Of course you could use variations of any of the methods mentioned, or there is something similar on ZDZ's website.