Hi

I have an aresti with an OS 70 supass 4 stroke and believe me its all the power you need. The balance is perfect with the 70, vertical performance is almost unlimited and all manouvers can be done as large as you want. I have had both OS 70 and 91 four strokes and I like to have plenty of power in reserve but would say that a 91 is way too much.

As for your friend with the warbird, the extra power with the 91 will help with that type of aircraft but you just don't need it with the Aresti. If you already have the engine, go ahead, put it in but be prepared to set your atv so you can only get 3/4 throttle otherwise you'll rip the wings off the thing.

As regards the weight question i could'nt tell you and as regards the question about the thunder tiger engines I would recommend sticking woth the OS, as far as I am concerned there is no better quality four stroke angine than the OS.

I have had my Aresti for about a year now, love lying the thing, fly it week in/week out. This plane along with the OS 70 I have is a great combination. I dont know if you have flown yours yet. If you have not I am sure you'll love it.

Hope this helps

Simon