The ys 110fz is the ticket for this plane , it will drop right in the same mount as the os 91 fs ....I paid more for mine because I had to be the 1st to have one in Alaska....BWHAHAHAHAHAHA....Iv'e heard that chief has them for 330.00 or so ..I'm swinging a APC 16x6 wide chord prop, it turns it with no problem, it could probably turn a bigger prop but you my have to put larger tire's on it for more ground clearance, I would also use the sullivan tail wheel assembly Not he POS that comes with the plane...I used a GP 1/4 scale tail wheel assembly that work's great but the throw's are not max because of the steering arm, the sullivan should allow you to max out the throw's with no binding.....I wish I would have looked at this site before I put mine together .....It would have been built different/better....I do have a spare that IS going to have all the mod's from day 1.....as far as cata,,,cata ....okay crashing , just remember they all have that dam exploration date inside .... Oya on THE DARK SIDE......JW