I had an OS .46LA and it was not an awe inspiring powerhouse either. There are a lot of engines out there that will out perform the 40 LA . I have heard the LA40 is one of the best .25 size engines around though. [sm=lol.gif]
Weight if a major factor with the Tower Trainer from what I have read(and you have seen) so keep that in mind. You may look at the Thunder Tiger GP42, it is one of my favorite engines and should out run the 40LA by a good margin and only weighs 13 oz. complete with muffler.