Hi Neil

Welcome to the forum, and all the best wishes for 2021, especially with your project to become a proud owner of a Macwester.

Having worked for Macwester Marine in the ‘70’s, and owned a 27 for 20 years until recently, I can put forward some comments about your project.
The 26 was the first popular twin keel model produced by MW, and broke ground compared to other designs for the sea keeping qualities and interior space. However due partly  to the deliberate choice of a shallow draft configuration, with a generous long skeg to give perfect stability when dried out, the sailing performance was compromised, especially to windward.
It is true that with a mainsail badly cut (foot too long, trying to increase sail areas), or not well trimmed, weather helm could be present. Techniques to counter this include accepting to reef the main quite early when heeled, replacement of the boom rolling reef system by slab reefs, which give a much better sail profile, and some even fitted a bowsprit to bring  the sail area forward a bit.

By 1970, the techniques of hull design using dynamic tank-testing (at Southampton University) led to the development of the 27. The ballast is profiled and shaped in cast iron bolted to the grp stub keels. The skeg was reshaped, to reduce drag, but still provides the “third leg” for drying out, without leaning on the rudder, as on some other makes. The draft is deeper, of course but at 1m17 is still very reasonable for “ going up the creeks”. Sailing performance is obviously much improved, as is manoeuvrability under engine. The rest of the design for interior space, lockers, deck design remained similar, for the first couple of years. The MkII updated the deck layout, and brought the lower stay chainplates to the cabin roof, making the side passage to the foredeck even clearer.

The prices between the two are now really more dependent on the state of maintenance and equipment, (original or replacement engine, notably). All Mac’s were very solidly built, and generally have  stood up to time better than the average. I won’t pretend to replace a professional surveyor, but apart from obvious wear and tear after 40 years or more ( or previous accident damage) , the most difficult issue is excessive wear on the bottom of the keels on the 26, after years of drying tidal mooring on sandy or other hard ground. Even that can be repaired with the appropriate skills.

Good luck with your search.

Don’t hesitate to ask if you have other questions.

Cheers

Bob.