RE: new vs. old slalom shapes
Q1 = Is it fair to say that the new wide short boards plane quicker and accelerate faster especially in moderate slalom conditions (7m sails) than the older narrow long boards?
A1 = Yes, in general it is fair to say that and especially around 7m.
Q2 = But that the top end speed of the older shapes is greater?
A2 = Not so simple; in fact (as discussed above) it's possible both in theory and practice for short wide (high A/R) designs to also offer top end advantage (c/w accel or mid jibe speed). This is most noticeable in smoother conditions (light to moderate slalom conditions and speed sailing on flat water). On the other hand, in rough open water, a slightly lower A/R (and less theoretically efficent) design could have top speed advantage.. But it would be an incorrect generalistation to say the older shapes have greater top end in all circumstances.
Q3 = So in a slalom race(again with 7m sails) with many jibes a wider board could easily win due to its ability to carry speed through the jibes and accelerate quickly.
A3 = Yes. And more, because we have significant testing of boards around the 7m size (~ iS101) which can show higher point to point open water speed, a lot more than just "effective speed" around marks and thru jibes etc. If you add in further real world variables such as improved rideability (ability to push the board hard to achieve higher top and avaerage speeds), relative ability in patchy or inconsistant conditions plus "upwind" ability (when required), then the overall result out on the water is pretty convincing.
( Practical side bar here : I can't think of anyone in our team who would now choose the classic benchmark Sonic 100 in that range over the iS101 for anything like slalom racing in 7m conditions)
Q4 = In hi wind slalom conditions(5.8 sails) the advantage of the wider board diminishes as control in the choppy conditiond suits the narrower board and speed through the jibes is less of a problem for the narrow board.
A4 = Yes, the advantage diminishes, however mainly because of rough water interference with maintaining an efficent fore/aft (longitudinal stability) trim across serious (hi wind) chop at high speed, rather than speed thru jibes etc.....
iS122 (for example) has a rather unreal hi speed pivotal jibe ability for any 12xLt or 75cm slalom style board, but again acknowledging a slightly different style or technique being optimal to that of the drawn out scalpel carve of a narrow, long slalom. In fact, what we found testing iS101/105 vs S85/95(S100) was that even when solidly overpowered in a straight line, the iS could still offer some advantage (suprisingly) in the jibe (with minor techique/style mods to suit) by carrying more power into and thru the jibe, with less precision required than a long narrow.
(advantages in real world use, especially the hustle of tight short leg slalom racing are pretty obvious). Now again, that doesn't make long narrow obsolete (esp for hi wind open water) but it does show the short wide advantage can encroach (in practical use) further into long narrow territory than maybe theorectically optimal.
(final footnote here is the short wide in question better have a good jibe, or this peripheral advantage doesn't exist...)
Cheers ~ Ian