I've never used the clips. I found that I just have to hold it up where I want it and get one nail in the center of the board. Then I set my level on the top or bottom of one side, put a nail in it, then do the other side. It's very fast and easy to do.
How are you setting the reveal?
The Solosiders set it perfect every time and I have been spotting the plank then moving the tools to that plank and finish fastening.
I have been checking every plank for level and haven't missed yet, but I have to know!
Those chimney pics show how not to install at a roof.
There should be step flashing and kick-outs.
Also I just checked the Hardie instructions and it says 2" gap above the roof/shingles.