If you can find an active offshore multihull fleet in your area, you can work in between their ratings. For example, all the F-boats have Portsmouth numbers. Florida Offshore Multihull Association has a website with PHRF numbers. My H20 fits in between F-25C and F-28R in Ports, giving me something in between their -15 and +30 PHRF numbers; say 6-8. I've done two "races" where I had a number in the 50's, given some formula type-conversion; what a gift :-) One of the races was against F-28Rs; don't know where they got it but they were using 66! Unfortunately its hard to find PHRF/Portsmouth links for boats faster than the F-boats; not enough of 'em to get either PHRF or Portsmouth. I think you could "guess" a number of negative 50-60 for a Tornado or Inter 20. If the wind is light, the big boats will kill you going dead downwind with chutes, especially if there's chop. Upwind in ANY wind (8+), you can walk away unless they're 50 feet or more. Mark, looks like these numbers are actually close for what you and Harry did last weekend (his number would be real close to the H20 of 6-8). Chris