Taking the flywheel off will move the CG back. But most trainers, including the Alpha, will often fly better with the CG moved back a little anyway. ("better" for someone who's soloed, comfortable with the plane, and looking for a bit more performance out of it). There are a bunch of things you can do to a trainer to make it a lot more sporty. Finding a prop you like, moving the CG back, increasing control throw, and reflexing the ailerons (raising both ailerons slightly) all together can really transform an Alpha or other trainer.