Hanoiboi, I'll post the cowl demension Thursday for you. A .90 is awful big. Whats your altitude. I run a Saito .82 and it appears to be the best set-up. The cowl is quite roomy inside but it's best to mount the engine inverted and run your exhaust flex tube out the bottem. Use a Dubro refueler and mount it to the bottem/back of the firewall. This really is one of the very best ARF's but it simply is not "taking-off" in popularity. It may be taken out of production soon,it's not even being advertised anymore either. Strange indeed. Seeya, MM