Thanks Gents, for all the good information!
I really appreciate it.
Interesting how many I-beam designs there are.
Argus, Cobra, Atom, Airon, Ballerina, and, as I recall, at least one very large one with full length strip ribs.
As soon as I get through a number of ongoing projects, I will start on the Cobra, possibly with a four stroke.
Bob Z.