A thing which always gives me nightmares, is coming down from high speed at the end of a long straight. If you don't know what the front brake is going to do, you always need to ride slower. Drum brakes heat up when they are used, and the behaviour of the linings changes. Sometimes, the bike can become unstoppable, and when the brake is held on, the linings heat up and suddenly grab. The last time it happened to me I had done a few laps in a winding circuit, and as I braked at the end of a straight, the bike over-braked in front of another rider. The guy is supposed to be mate, but he decided to play 'tit-for-tat'. The idiot got in front of me and got inside my braking distance. It was the only incident in which I seriously believe I could have been killed. It was the reason I sold the bike back to the guy who had originally built most of it.
Drum brakes and pudding basin helmets should never be used on a fast bike on a racetrack or on public roads.