First, the idle seems a bit high to begin with.
Have you tried adjusting the idle speed when the engine is warmed up?
Next, the hot idle compensater may be opening up when it gets hot. It's basically a controlled vacuum leak to increase the idle speed slightly when the engine gets hot. It uses a bi-metallic strip.

Cliff says they aren't needed and the port can be plugged off with some lead.

Your hot idle sitting in neutral should be between 600 and 700 RPM's.

If you haven't purchased his book, I highly recommend it.