All engine bashing aside. I too just bought a Twist and am putting a YS .63 in and it fits "slicker then snot on a doorknob". On the other hand if you read some of the posts on this plane, they are saying that the Saito .72/.82 is a tight fit and someone said they would have to remove the cowl cheeks to do it. I am also considering putting the fuel tank on the CG, something I don't think you can do with the Saito, without a pump.

Besides all this I have another YS .63 in another fun fly type plane and I got to tell you this engine is just awesome for FF type flying, incredible power and instantaneous response, 100 flights and not a bobble or a deadstick.