It seems that this discussion adresses at least 2 different questions:
1. Which boat is the fastest around a race track or on sections of a race track? (disregarding the crew-skill factor)
2. Which boat can reach the highest top speed?
The latter question raises the problem of measurement method. The GPS-method is simple, but Wouter here points out questionable reliability of the method. I suppose the problems orginate from conditions when more than 3 satelites are not received continuously?
My Magellan Meridian color used to produce erronuously high numbers before fixing a bad contact in the power circuit. With a 1-second update period, it now seems to be accuarate all the time, based on comparisons with numbers on my car speedometer (with known rather constant error).

Can anyone give us information on how to get reliable speed data?!

Stein