I clearly respect your experience with the venerable and famous BlueBird. She was truely a remarkable and innovative design. But she has very little resemblance to the Westerly's in question.
I will say that it is rare to have a chance to do months of side by side testing of different keel types on otherwise identical boats. My experience was with fin vs bilge keel versions of the same boat and essentially the model in question. My experience was across a wide range of windspeeds and in multiple groundings and that is the basis of my comments.
There was a very observable differences in speed and handling between the two models in questions. Since the sails were rotated between boats for a variety of reasons, but mostly because we taught new sailors to rig the boats from bare, so that sails did not make a difference, neither did which instructor was on board. I was one of the faster sailors amoungst the group and when sailing the bilge keel boats, I could not keep up with the slowest instructors on the fin keel boats, but I could easily run off and leave them when I was on the fin keel boat. One of the other more experienced instructors and I experimented sailing side by side on quite a few occasions, and the bilge keel boats clearly made a combination of more leeway, less speed, and could not point as high. (I say combination because you improve pointing angle a little but speed disappeared and leeway increased or head off a little and get a little more speed and less leeway at the price of pointing lower. Even so the fin keel boat was better at all three.)
While a bilge keel boat does not have to be less stabile, achieving an equal stability to a fin keel comes at the price of a combination of higher drag and more weight.
With regards to the grounding issues, I have seen versions the diagrams shown above. In reality, the Westerly's do not have BlueBird's widely skewed keel angle. The keel tips are closer together and at normal sailing angles the leeward keel was not all that much further down than the windward keel. In a grounding the leeward keel leveraged the windward keel into the bottom jambing both and making rotating the boat very difficult. We used these boats to teach how to free yourself from running aground. Whatever the throry, after dealing with the grounding problems with freeing the bilge keelers (even using the Boston Whalers to help tow them off) we stopped using them to teach freeing the boat from a grounding.
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Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay and part-time purveyor of marine supplies