Darn TIA, you offered all of the solutions I was thinking through the post. I don’t have a yawl but row my dory often, no one has chimed in so I’ll give it a shot. A deeper skeg would help the stern. If you add a full length keel you’ll sacrifice a lot of maneuverability and add some drag. Usually the bow is pinned by water pressure down each side but with your weight you don’t have the sharp part in the water as you say. I think your best bet is to experiment with the least amount of ballast you can get by with, 35-40 pounds total gets you up with the rest of us. Experiment with placement fore and aft, depending on which quarter the wind is on. Down on the floor is better. Also, having half and half at the far ends might not be best. The weight out at the ends will change the turning moment and may tend to increase fall off. This is counterintuitive. You may try something like tacking with the wind. You’ll row further but might make course holding easier. Finally, the rudder idea is intriguing, Maaaaybe something like a kayak rudder might be all it takes.

Or, join the rest of us and gain weight ;-p

Cheers,
e

Thank you Silver Salt,

(BTW, "TIA" is not a screen name or anything, it is my understanding it means "Thanks In Advance" and usually culls more responses on these boards than rude expectation that one's post DESERVES an answer <grin>)

Anyway, I agree about a stem to stern keel hampering maneuverability and was hoping for another solution. I experimented today with just one bag of rocks (literally) weighing 30ish lbs. Wind was a tad strong at about 12 -14;  whitcaps just forming, waves in the 12 - 18 inch range. With the bag-o-rocks initially placed far forward on bow seat, the stern was now being pushed by wind. I guess that indicated overcompensation - a good start. Moved the ballast onto the floor snuggled against the fore seat thwart and rowed about 15 degrees off the wind. Now the bow was being pushed off the wind. Looks like the sweet spot is somewhere in between. 

I have a feeling different placements

will be needed for wind strength and heading. Do not think it will be easy moving 30 lbs under way.

I just finished my Chester Yawl recently and I have only been out once, but I had the same issue with weathercocking. In my case, although I way in only 5 lbs more than you, I also had my wife with me and I still had problems if I wasn't headed directly into or with the wind. When I have two people in the boat I use the forward rowing position. My wife started out on the very confortable rear "seat". That had my bow too high so she moved onto the floor. While it was less comfortable for her, the trim was better and I had less trouble with the wind pushing the bow around. It suggests that I would have been better off putting the forward oarlocks even farther forward although there isn't a lot of room for that.

So, I take from this that adjusting the trim is more important than the weight in the boat.

Two thoughts - both of which revolve around making the boat tip/tilt/carve into the wind 

1) adjust your oar handles position so the windward oar is lower than the other

2) Shift your weight off of the ceterline of the boat - twoards the windward side, again to make the boat tilt/carve into the wind.

When I row my NE dory with in a crosswind,  I first lower my wind-facing oar handle. This forces the boat curve to into the wind ever so slightly. Along the same lines shifting your weight in the boat to the windward sides also can help. This is most dramatic if you are rowing an open water racing shell (I row a Echo www.echorowing.com and the effect is dramatic), but also useful in the case of my NE dory - and hopefully in your case as well. I should say though that I do weigh 200 pounds. 

This kayaking page gave me the inspiration. 

https://paddling.com/learn/weathercocking-handling-beam-winds-in-a-sea-kayak/