ORIGINAL: jsenicka
What 91FS?
The Saito 91 is identical weight to the OS 70FS and makes a fantastic engine for the U Can do 3D 36, or the Funtana 40 or the other 40 size 3D birds mentioned here.
The OS91 is 3 or 4 oz heavier, so you need to watch weight
The saito 91 I have on my Chak balanced with no extra weight and it didn't come out heavy. I only have to move the battery around in the wing to change CG. Most are putting saito 82s on them, and either add tail weight or shift the battery to the very rear of the wing.
Sure it's a little overpowered, but it's there when I need it. Yeah I know most everyone likes a full fuse, but if you're really wanting to practice 3D, a profile, that is set up correctly, is hard to beat. OMP has some nice profiles. Also mojo 60s are easy builds for that winter project.