I have a K&B .65 that has ssen a few hours, not yet worn out. It was a later date I think like 95 +- a year or 2. idled and transition well. OEM carb. Going in my current rebuild project. I have proped more like a 4 stroke and in it's current ride propping it just the same. I have hade 2 K&B .20s and 2 .45s. All that is left is the .65.
I have used 12x6 and 13x6 on mine perfer the later
They get a lot of direspect, but I find those who do just don't understand the engines or try to use them in planes that they are just not suited for.
I remember seeing thos drones in the mags way back when.