This is what I was looking for. I kind of thought to do that, but just wanted to make sure I wasn't way off base.
Now the next question that was raised about using starter on one level and J on the other... not sure about that one. I've never done vinyl so I'm not sure why you can't use starter on both levels? As long as I measure and make the vinyl over the door meet at the same height, why can't I use starter on both levels? Or am I mis-interpreting?
I don't know why you wouldn't use starter at the bottom of both sides of the door? You'll just need to make sure you are a full course (or more, not sure what width siding you're using) below the starter on the left side of the door so it meets up properly once you get above the door head.
Siding is a given width. The only way you could use starter on both sides of the doorway is if the bottom of each side of the opening is the exact same given width of the siding. Chances of that happening are very slim.
For example, you use "double 4". so your bottom of your piece to your lock at the top of the siding is 8"....the dimension from one side of the door, to the bottom of the opposite side of the doorway would have to be 8". Any dimension that differs from the 8" needs to use a "J" channel so the top of the siding remains level around the perimeter of the garage. At a door opening, it would really stick out and look like a hack job. plus the fact that once you get to the top of the doorway, you will have to have the siding line up.
The only way you can get by not having things line up correctly is for instance where a back wall and a side wall is broken up by your corner piece. But even with that, if you are off any more than a half and inch, it will really show.
You can cheat the siding a little bit by pulling one up tight or leaving it a little more loose, but by all rights, if you get your level line around the perimeter, you'll see where you have to use a starter strip, and where you have to use a "J" channel.
Any place that you buy your vinyl siding at will have complete instruction sheets that they can give you.