Doug Ward worked for Columbia. Here are some of his comments on the differences/similarities between the Columbia 26 MkII and the Coronado 27
You are spot on regarding the differences / similarities in the Col 26 MK 2 / Cor 27. The major hull difference is at the stern, where the factory (singular) simply added about a foot to the stern of the 26. The O/B well was deleted, & a removable "plug" was designed into the transom. It was actually a cut out section that was keyed & finished so that it simply dropped into place when the O/B was removed. There was no transom plug in those boats that were ordered with an inboard engine. There was another difference, too. The companionway steps were not moulded in, as in the 26. They were made of teak & removable, to expose a small " engine room " in that area. There was also a moulded in pair of engine beds that the 26 didn't have. There were more 27's ordered with inboards than 26's The 27 had a larger cockpit than the 26, also. When a 26 was ordered with an inboard, it was usually an OMC Saildrive. The 27's got the little Ferryman diesels with prop shafts, etc..I can imagine that the 27's had the same problems as the 26's do when the O/B is mounted on a stern bracket. ( Pitching / prop cavitation, etc ). 26's much better with the O/B in the well & 27's better with an inboard. The 27 does sail a little more civilized that the 26, as you described, because they are a little heavier & have less sail area. They both are a handful in a following sea because thats just how those trippy little jobs are. Regards, Doug Ward.