I had the vertical stabilizer come loose on my Alpha 40 as well. I epoxied it on with tri-stock supports on each side. I also epoxied the horizontal stabilizer to the top of the fuse. Shortly after that, my stabilizers came loose again, during flight. I was able to land it, and found that the top part of the fuse, where the stab was epoxied, came loose from the sides of the fuse. I ended up adding tri-stock below the horizontal stab to reinforce the connection to the fuse, and it has been solid as a rock ever since.

Congrats on flying your "60". It is a great plane to train on.