Getting more aero and cornering better are what you do. I'm not a heavy rider, usually 148-158 lbs. but am a somewhat famous local descender. Heavy people can't get near me. I think it's partly my build (I have short legs) and partly because I used to ski downhill and so have a good feel for aero and don't mind speed. It's all about getting tiny, thus reducing your swept area, and about getting rid of stuff that catches the wind, like your arms, legs, chest, etc. Rolling resistance matters. Bike shape doesn't seem to matter much. Wheels maybe a little, but nothing compared to position and cornering ability. Hubs don't matter at all. Weight doesn't seem to matter much, I think because heavier people have a hard time getting rid of drag and maybe as was mentioned above, they accelerate more slowly. I also stop pedaling sooner than many people. Pretty hard to overcome the drag of your legs being out in the wind and having legs pop your chest higher. On the usual "spin-out" grade, I'll stop pedaling at around 35 mph.