Bob,
What you said sounds correct, yes 20 amp was the size fuse. I remember pulling the 15 amp out and upgrading. Sorry I didn't take any pictures to share.
Another item I have implemeted is Water Wetter. Get it a our local auto store, add to your water/antifreeze (follow directions). This lowered my guage by 10 degrees. Don't know how, it's a chemistry thing and works.