I've been give a copy of the above plan.  It has no reference to date of origin.  Walt's autobiography mentions contributing to that magazine as eary as 1947.  The engine shown is an Ohlson 23.

There is/was a newsletter for the organization called Kits and Plans Antiquitous, KAPA.  Their June 1997 edition had the story about Walt Musciano, from his boyhood to the then present.  This amounted to about 45 pages of information, including his story and a number of pages showing various plans and pictures published in the magazines.  In that material was a listing of all of Musciano's designs, articles, books, published drawings, kits, etc (needless to say, this was an extensive list filling 8 typed pages, single spaced).  In that listing was a scale drawing of the Curtiss Hawk, P-6E for CL, 1" = 1', with a 32" span for .19 - .35 engines published in Mechanics Illustrated.  The month is not given but the year was 1949.

I have gone on line in the past and obtained information on MI back issues and was able to purchase a copy from 1948 in excellent conditionwith which had a scale Sam Calhoun Smith construction article.

Hope this helps.

Keith

The Navy used a slightly different version of the P-6, the F6C, the F6C-3 looks similar but has significant differences. Walt published a plan of the P-6/F6 series in MAn in the 1953. It shows the difference in several versions, mostly in the nose area. I believe the AMA sells the plans. The F6C-4 was a radial. Attached is a piece of the plan.
John

yeah -- F-6 with radial became XF-11 develement