The Primo is very aerobatic and 3D worthy and on low rates will actually do some nice pattern.

The new motor mounts are a ply/balsa/ply sandwich with hardwood rails for the engine to mount in. You may need to widen the rails just a little. Much easier before it is glued up. It will be easy and you will like at the fuse on paper and be surprised at how fast and easy it goes together. As for strength, its plenty strong as-is. I have one with a YS115 and its plenty sturdy.