"I don't think many new modelers building Scientific kits would convert them to beam mounted."
George, you make a very good point there. I had not thought of that.
Still the tank was an option and surely there were radial type mounts ala Tatone and the like? The tank fit both the 07 and the .049 and was available seperatly (see pic).

Scientific had a couple of larger 22 inch span planes and who can forget the wonderful CG Jumpin' Bean? I bet that would have been OK.
The Monarch Spitfire and P40 models were up to .099 and had beam or radial mounting in the kit.

Honestly I did come along in modeling about ten years after the Stunt Runt and Fox 07 were introduced so I can't speak from personal experience as you can about that time period and now I have the more experienced mind like yourself. I bet it was different then to beginners. Besides you could get away cheaper with the Cox 049 and that I believe is why the Fox 07 coulden't keep pace. It was about 2 dollars more and that was about the price of a kit! Well almost.

"Berkeley kits... Everyone should have built at least one."
Sad to say I have never had one. I have seen lots of pictures. Some more impressive than others!

Robert