Having an Alpha in my "collection", and having hand launched it several times, for no other reason than tempting fate, I would not suggest launching it at a 20 degree angle.
Maybe 5 max, and as suggested, more like level. Having said that, I'll ask, do you really NEED to?
It will help if you have hand launched a LOT of planes, and use an 11X5 prop for maximum thrust!
Don't forget, it weighs a bit, and will be covered in oil.
Good luck, and don't expect miracles!

Jetts