"Weather Helm" is an interesting phenomena on a sailboat. I cannot disagree with anything posted. Reducing the rake, or angling the top of the mast more forward, has to reduce weather helm. Proper trimming in stronger wind such as spilling air from the main will also reduce weather helm.
But, I believe there are factors other than rake of the mast or trim. Boat design or improper boat design can cause an excessive weather helm and there's little that can be done to completely reduce it. Shape (or lack of shape) and location of the keel are also important factors.
I currently own a Seafarer 29' with a swing keel. Of all the boats I've owned this S29 has the most balanced helm I've experienced. I've sailed it with main alone, and with a 150% genoa alone, and there is little difference in respect to the helm.
Contrary to this example, there is a Cal 34' on my dock and the owner is complaining of a terrible weather helm. His mast doesn't appear to be raked too much, but we have discussed adjusting it too see if it will make a difference. It would help if he had a backstay adjuster. So far the only thing that has noticeably helped if he spills air from his main until the helm is balanced. Unfortunately, this is probably costing him some SOG.
Here's a quote from a post on Wikipedia about weather helm, " the root cause of the phenomenon is the relationship between the center of the force exerted by the sail plan, and the center of the resistance to that force by the hull, and not the angle of heel of the hull."
We assume that all boats and designed and tested by competent naval architects, but in Venture/Macgregor's situation back in the 70s who knows? What if cabin comfort is slightly sacrificed by locating the swing keel a few inches forward of it's best position for balance?
Here's links to a few good discussions and posts on this subject.
http://en.wikipedia.org/wiki/Weather_helm
http://www.endeavourowners.com/dscsn/handling/wthrhlm.html
A comment on this post supports my position that a serious weather helm is most likely a result of the boat's design. Post from May 12, 1999, " I spoke with Rob at the Endeavour factory (he was there when they still built production boats) and he said even if you take all the rake out of the mast you can not tune out weatherhelm. He said people have had great success putting on a bowsprit and moving the headsail forward a couple of feet."
This is a great article on SailNet about "balance" in general.
http://www.sailnet.com/forums/seamanship-articles/19146-balance-hull-sails.html