I dunno, but I'm hoping one of the naval archs weigh in here, because it's always been my thoughts that rake contributes to weather helm... more rake more weather. But I like you was told more rake for my masthead rig, between 8-14 inches! I started the season at 6 (because there is conflicting rig tune data on my boat, I guess depending on who made the sails).... but anyway, managed to pick up a significant amount of performance later on in the season when I changed out to 14 inches of rake.
Doing this added more weather helm to my boat for sure, but not horribly so... by my thoughts were that weather helm (excessive) was REAL bad due to stalling of the rudder.
Digging across the net, the best I think more rake gets you is slightly better windward performance.
Again, good question and I am curious to hear responses.
But then you get people saying "she likes to be sailed flat," but nobody wants to define "flat." Watching GPS and knotmeter for a year now on this boat, apparently FLAT is anything that keeps the stanchions from getting wet.