RE: Avistar or tower hobbies trainer?
For this application anything more than standard servo's is overkill. The only suggestion i would make is be sure thy are ball bearing servo's. As to what engine. Any decent 45-6 would do. I like Irvine, ThunderTiger Pro, Super Tiger, MVVS to name a few. Buy a decent brand name and you should be fine.
Mark Shuman