I have iron heads on (for now), sometime later on this year I will put the Dwayne-massaged Speedmasters on. Good quench for both.
The most initial timing I could run with good hot starting was 22 degrees. At 24 it would begin to fight the starter sometimes.
Plugs are light tan BTW.

Time to get a better fuel tank sender, too. The foam float in my current (vertical sliding) one is hard and brittle... and with the tank full to nearly the bottom of the filler opening, the dash gauge only reads 3/4! Yes, I have the proper resistance (240-33 SW gauge). As thirsty as this beast is, I want a more accurate gauge.

Thanks for the comparable data points, everyone. Today I went and got some more gas in cans, and filled it up actually slightly further than before, one 2 gal. can and there is still a gallon left in the 2.5 gal can. So it actually used 3 to 3.5 gallons (not 4.5) for 21.9 miles of blasting around. That's more like it (6 to 7 mpg), I can live with that.

Will report back once I put a few more highway miles on it. Now to clearance the #2 header tube where it's rattling against the shock tower...without removing the header