I would include the OS .40 LA -- not that it is a really bad engine, but it is gutless & much too expensive for what you get. The .46 LA is the same size & weight ,but noticeably more powerfull & is only a bit more costly (although it too is not really much of a bargain).
Whaddaya expect for $55! And to say to avoid this engine is.......well.......bluntly........BS! OS has some of the best engines going - not only for power but just as importantly - dependability. Ya can't expect this engine to perform like a FX or SX version and if you buy it for that reason then.......bluntly.......you really screwed up!
As stated in this thread - the OS 40 LA is basically an inexpensive way for someone starting out to get their trainer in the air - and that's about it. A bargain - you bet it is. Why? Because it serves the purpose for which it was designed and for those countless thousands that started in the hobby and then decided not to stick with it or for those that trashed their first trainer - they were not out megga bucks in the process.
The only reason I am even responding to this post is so others starting out with a 40 size trainer don't go out and spend more $$$ than they need to thinking that you know what you're talking about.