I have a pimped out 5.8 - since the 6.0 was based on the 5.8, some of these observations probably apply.

My main is a Glaser squaretop, same area as the original, but essentially with the lower triangle moved to the top. The jib is the same size as the original, but I tack it to a NA foil - longer luff, shorter foot so it self-tacks. I also run a kite, slightly larger than an F18 kite.

Despite the fact that the main and jib are the same size as original, I take the 5.8NA number as the base handicap, on account of the foil. Then add on an MN and SP adjustment.

Maybe that's fair, maybe not. But it's actually never made any difference. We usually check the results both ways, occasionally taking the Original vs. the NA will change a position in a race, but never in a regatta. It's a good exercise to do if you're worried about handicap ratings - Take some race results and see how low your handicap has to go before you drop a position in a race, and how high it has to go before you go up a position. If you're anything like us, the range is surprisingly large.

I didn't plan on racing the 5.8 this year. However, since wrecking the Nacra CF20 in the GT300, we pulled the 5.8 back out and have done several regattas in it while waiting for parts. Since getting back on the 5.8 I've noticed that it is really lacking in buoyancy compared to newer designs. It doesn't make much difference downwind on VMG angles in less than 15 knots or so. But if we have to hold the kite on a high angle, or go downwind in big air we can't quite hang with the F18s despite having a longer waterline and more sail area. The 5.8 just maxes out, and more power mostly just puts more hull in the water, while the newer designs still have some speed to pile on.

I never really thought about the lack of buoyancy since the 5.8 doesn't really mind being driven with a hull underwater, but that doesn't mean its fast.

I don't regret re-rigging my 5.8 at all. It's fun, very forgiving, and fast enough that when racing F18s the better skipper will usually be first across the line. But there have been great things done with hull designs since the 5.8 and 6.0 came out, and they're well worth taking advantage of.