The Morgan is of reasonable weight, has a small efficient tapered wing with large flaps, flat bottom, there's plenty of them out there, they are based on the KR2 also with proven history/flight characteristics, and Morgan owners seem more than happy.
What's your experience exactly? Can you support your disputing claim to the manufacturer's with some facts?
Everyone should always be on their toes with manufacturer's claims, but when you call them out you need to back up your claims also.
Carbon Fiber is certainly the most efficient, at a large cost though, but fiberglass isn't.
Wood is still 2nd only to CF (and even then balsa wood is still the strongest laminate for composites), and aluminium is still a better weight to strength offering than fiberglass, as is rag/tube.
There's good reason the big 3 kit planes, Vans, Zenith and Sonex, choose aluminium. Lets not even mention Cessna.