You are absolutly right, a lot of designs on our PS12 came from airmodeling and boating and if you read all my posts I am always say it. I will repeat one more time- I am orriginaly from Soviet Union. Since 1976 till 1993 ( I left USSR) I was making tether boats 15 engines with air propeller and 60 engine with half submerge water proppeller. On the beginning of my hobby carrier I was flying control line speed models, but in 1979 concentrated only on boats. From 1993 till march last year I was doing nothing in hobby and never think will come bak. But my son push me back and all my work didicated only to him. Whatever I do in hobby it is my hobby and actualy I don't make any money on it. So I have been in RC cars just about one year, that is all. But I work with engines since 1977 ( 27 years ago).
Now about the design-yes here is some engines with sleevles design, but not only in air modeling , also on lawn movers too. Yes a lot of russian engines don't hve inner ring on main bearing and I use the same here ( why would I do different if this design is the best?)-so what is wrong with that? Sirio innovated cooling fins on sleeve and brought it as new design-yes it is for RC cars, but in general first this design was using on Russian engines in earlier 80's.
I came from Russia and belive me, if I got involve in hobby, I will bring here what ever is newest and the best developed regrdless is it in airmodeling or boating or RC cars. One more thing, I got pretty good results from the stuff I have already brought.
So what is the point on your post?
BTW sleeveles design in airmodeling is made only on one brand ( in mass production) and it is 40 size engine, and belive me to make the same design on 12 size is quete different and if you familiar with tehnolgy you will know that cast AL alloy with wall that our thikness with no micro air pockets ( affecting chrome plaing) isn't that easy and similar as on 40 size engine.
Wow, I am done