I've seen a few go from heli to planes and they picked it up pretty quick. But like was said, the beast is a pretty big jump. On the other hand, the cub might not interest you for too long. A low wing might satisfy you aerobatic urges and be more stable. I usually recommend a .60 (or .40) sized ugly stick as a second plane. Very utilitarian and has a wide flight envelop. Any size in the 4-star series would also be good. I dont fly 3D so I cant recommend anything beyond that. I'm assuming here that you will want to go the 3D route. The three guys I've seen go from heli's to planes are all 3D flyers. At any rate, the first plane you get wont be the one you stick with. Most all of us have a beater to test equipment in.
Edwin