As the boom is to leeward this force pushes up from the leeward side of the boat so there is less resultant force pushing the boat over. Equally the more power required the more upright the mast should be set. The mast may only go upright to the point where the helm has still got a little weather helm. Much more mast rake would generally be required above 12 knots. The amount of rake will be proportional to the amount the boat is over powered.
Spreaders are the key to power in the mainsail.
The straighter the mast is, the more depth will appear in the aerofoil section, so increasing power output from the main sail. If we return to the idea of maximum power required when the rig is only just up to full power and the crew not fully stretched- when the main is sheeted in hard the leech telltales should just stall. In lighter winds this may only be intermittent. Therefore, if the tell tales need much encouragement the sail is probably to deep, if they always fly it's too flat. Franck Cammas's trimaran is 16 miles ahead of Foncia-Kingfisher of Alain Gautier.