Dear Wouter, why do you constatntly say the sailarea on the A class is rather small and uses that as an explanation why it has no jib? In relation of sailarea/weight the A cat is having the most sailarea compared to it's weight of most of the boats discussed. For the same reason, at 1bft adding a jib might increase the upwind speed of an A cat, from on +2bft I am pretty sure the jib will slow you down as you are fully powered up already without anyhow. Downwind a spi is more efficient than a jib, so if we discuss outside class restriction, with any boat you would go for a spi.
F18HT shows it as well as the earlier Ventilo 20 (which regulary outsailed the Tornado).

A cat 75+75/14 (m²/kg)=10,7
F16 uni 105+75/15 (m²/kg)=12
F16 sloop 105+75+75/18,7 (m²/kg)=13,6
C Class 130+75+75/25 (m²/kg)=11,2
F18 180+75+75/21,1 (m²7kg)=15,6
Carbon RIB (for Rolf) ;-)
M32 ?