I have unlimited vertical with an OS .91fsr. This is a little heavier than the .91fx. I would go with the OS .91fx unless you want to spring for a 4 stroke than the OS .91 or Saito .91 or 1.00 would be good choices. I originally had a Magnum .91 4 stroke but yanked it out for the 2 stroke OS. You will enjoy this plane alot! They fly very well. Look at upgrading the hardware though to something better. Hardware is flimsy. Good luck with it!