Wouter,

there is probably very little to gain by having a curved mainbeam. I suppose they are out to stop "somebody" with the right funding from doing all sort of crazy stuff. You know how the psykology works in this, 'pro sailor X is doing this, so to keep up, I must do the same' and so on. It's silly, but I guess this is how the F-18 rulemakers think and what they want to limit.