The Pacific Boats Olson 911S was based off of the earlier Capo 30. Primary differences were a the Olson has a different cockpit, slightly shorter rig, elliptical foils, and a nicer interior fit-out. Ericson changed the hull to solid layup, revised the keel structure, and put their own spin on the interior fit-out. There were approx 8 Capo 30s, 25 PB Olson 911S, and 51 or 52 Ericson/Olson 911S.
On the Ericson side, there is an early ad for the boat calling it the Olson 30S, but I'm glad they didn't go that route as it would have made things even more confusing when searching for information now. There is also some confusion on the SE designation with some claiming all Ericson built boats are SE's or it was a trim package that was set up as more racy than the S, or vice versa. I've never seen anything official from Ericson that mentions SE though. Seems like the PHRF board's generally refer to the Ericson built boats as SE and the Pacific Boats as S. About a 6 second difference in ratings depending on location.
As far as other Carl Schumacher designs, the Olson 911S is very similar in styling to the Express line of boats built by the Alsberg Brothers Boat works. The Express 37 and 34. The Express 34 is often compared to the Olson 34 in terms of similar design and performance. Also a good chance both 34's put Pacific and Alsberg out of business. Too expensive to build/develop, not enough profit margin.