I remember Rebel at the 1984? nats at Hayling Island, and being very fast ( ie a leg ahead ) in light wind races.
It was a very low wetted surface, high rocker banana boat with a lot of curve in all directions - very fast in light wind/displacement performance, but slow planing.
At Newquay it was leading for a while in races that started light, but as soon as the breeze came in, it got overtaken by virtually everyone.
I also think it has gone to add to gloabal warming. ( ie burnt ).
And no the P7 was a different concept - it was designed to plane early, so the opposite style of section, with a very flat floor. The rig was also designed to be powered up early ( 75:25 main:jib), with a bendy but 2 spreader rig, sailed by relative lightweights - so in an 'average wind' up to 12ish kts was superfast and early planing, pointing high upwind, and low downwind.