Run a front brake and use it whenever you need to keep your legs below a certain speed. Letting the bike get away from you without any fore/back pressure can be pretty wild at times - don't blow out a knee. I've come close to spinning out a bunch of times in Toronto already (my max seems to be around 33mph/55kmh with 46/17) and it's not so much fun after a few seconds

Having a brake is worth it for being able to modulate/hold downhill speed steady.