A truly remarkable airplane especially is generously powered. When will someone like Tower make this generally available again. Afterith seeing how well mine performed with an OS 25FX I refitted mine with an OS FX32. The results are fantastic...very fast while retaining all its agility, unlimited vertical with an apparent speed (remember it is small) that I would call blinding. I don't think extra spar length is necessary but the spar ought to be strong and must be well glued because I have seen one that wasn't come unbolunded with unfortunate consequences. I use a carbon fiber reinforced spar and when I put my next one together I will use a carbon rod or tube. Full length ailerons are unnecessary as you can get blinding roll rates with the stock setup. Also I have done full power dives from "speck" heights with no hint of flutter or other vibration. During combat I also flew mine into a tree turning into three pieces but with a little probound it was in the air the next week. I think the OS 32 SX is the optimum engine for it although my fellow club mates who use 25s and 15s don't want to fly with me anymore because the alienator with a 32 for outstrips the other configurations. As far as rudders are concerned I con't install the rudder servo to save weight. A fellow club member replaced the tri-fin design with a single large coroplast (sp?) rudder. With an aft CG I personally am not capable of handling his modified alienator does incrdible slow speed aerobatics. especially a range of flat spins.