Hi Ray,
I believe the Mangusta DR .049 drum rotor engine is a part of their custom engine business and the other type of engine is their regular product offering.
I noticed that he did some work for Larry Renger on an older Cox engine model so Larry may have some idea about this gentlemans work. This gentleman is in Concord, NC which is only 40 miles or less from where I live which is one reason I took note of his website.
I guess the Mangusta would be like buying a "custom level" of engine like a PA- 40 ultralight from Randy Smith instead of having Randy sell you a reworked stock type of engine like an OS LA-40. This is not a perfect analogy but I think it gets the idea across.
Given the time, energy, thought and effort this gentleman has devoted I would say that he is serious about Cox engines. I guess the practical question is; does it have the performance to move beyond just being a unique collectible and become a usuable everyday engine.
Anyway, these are neat looking engines so I wanted to share with the forum.
Pat Robinson