Power to weight ratio varies over time as well. Smaller guys are great at climbing long distances, because they can maintain a higher power-to-weight ratio for an hour or longer. Bigger guys tend to be sprinters (Chris Hoy is 205lbs) because their peak power can be much, much higher and compensate for the extra weight. For a one-minute effort, I'd suspect that a somewhat heavier sprinter profile would be an advantage over a lightweight climber profile.
Even moreso because the weight of the craft will be a smaller percentage of their overall weight. A 150lb cyclist capable of outputting 10W/kg for a minute will have an effective 6.6W/kg on a 75lb craft. A 180lb cyclist capable of the same 10W/kg would have an effective 7.0W/kg on the same craft. And a 180lb cyclist capable of 11W/kg would manage an effective 7.7W/kg.
Even moreso because the weight of the craft will be a smaller percentage of their overall weight. A 150lb cyclist capable of outputting 10W/kg for a minute will have an effective 6.6W/kg on a 75lb craft. A 180lb cyclist capable of the same 10W/kg would have an effective 7.0W/kg on the same craft. And a 180lb cyclist capable of 11W/kg would manage an effective 7.7W/kg.