Think back to senior school.... lets science the S#it out of this
;Like a moving car, the heavier the car and the faster its going the harder it is to slow down and the less it wants to change direction, (basicly heavy car = bad cornering, or light car going very damn fast = bar cornering)
This is due to its calculated kilogram-force or foot-pound force in old English.
www.1728.org/energy.htm +
www.convertworld.com/en/torque/foot-pound-force.html 2kg foil traveling @ 45km/h = 15 Kilogram-force metre (147 NM touque)
4kg foil traveling @ 45km/h = 31 Kilogram-force metre (304 NM touque)
Only 2 kg difference in foil makes 15kg difference at higher speed in what you are ACTUALLY trying to control.
Trying to control/change direction/pitch/angle,(with your feet) something that is 15kg vs 31kg makes a big difference to the feel. Yes you can control both but one is much easier, more responsive and less effort.
The same counts for the whole setup.
Our race setups are light, my foil & board setup is around 4.5kg total (i think)
4.5kg foil & board traveling @ 55km/h = 53 Kilogram-force metre
If i were to take a heavy setup likes of a older TKF foil & board setup at over 7kg,
7.5kg foil & board traveling @ 55km/h = 89 Kilogram-force metre (874,5 NM touque)
Lighter foil & board = more responsive
Heavier foil & boar = less responsive ( which can be a good thing in the first few days of learning)
A heavy board for the same reason is much much harder to to learn to tack as the weight + speed + swing weight is damn hard to control.