Distributor, distributor drive gear / Timing

I've seen the points issue 273 and rusty described many times but have one other question for you. When you installed the new timing chain and gear set are you absolutely positive you got the dots on the gears aligned correctly? I use a straight ruler or straight edge to eyeball it with cause sometimes it's hard to tell with the naked eye. Another thing, are you disconnecting the vacuum advance when you try checking the timing? If not you need to