I did an interesting HFTA analysis on W3CRA's site. Did antenna height calculations starting at 30 feet up to 100 feet at a 10 degree bearing, and the best height was around 70 feet. Plotted 68, 70 and 72 feet last and I am impressed with his choice. Would like to know exactly how he arrived at 70 feet or so. Don't think it was luck, maybe he did some crude ray analysis graph work by hand. Attached is the three height plot.

Courtesy of K3RU