RE: 4 stroke .81 size Os or Saito?
And I think you should fly something else between the trainer and the Cap. Doesnt matter how good you get with the trainer, the Cap is a big step. If you are confertable with your trainer, your 2nd plane should be a good low wing "sport trainer" type. Take a look at the Pulse 60 from Hanger 9. Great 2nd plane.
When you do fly your Cap (eagle 580) keep your air speed up and land a little faster. DONT try and "float" it in like your trainer.
One more thing, put two fat black stripes on the bottom of each wing. Makes it MUCH easier to keep your orientation.