I have 2 alpha's with the engines mounted like yours, they work just fine. Plant one on its nose, and the motor "slides" some in the mount, removeing a lot of energy from the mount and the firewall. Check the bolts for tightness once in a while, every other time you take it to the field, I have used my alpha's for 3 years now, and have only managed to get loose 1 time in a year. About 3/4's of a turn was what it took to cinch it down. If you bend the strap, just tap it flat, or put in a vise to straighten it. You will find your alpha to be a fairly forgiving bird in practice. Just start with your control throws down a little, you can increase them as you get familiar with the plane. It only takes a minute or two to adjust them.

EDIT- I hadn't looked at the picture when I originally posted. Ya.... Ya gotta get rid of the screws. Are the straps being pulled off of the mounting tabs on the engine? The curved portion of the stap should be mounted toward the engine case. Are the mounting tabs on the engine too narrow to fit the mount? If that is the case, I would replace the mount as described above. It isn't that difficult. I would also get rid of the phillips head screws, and replace them with socket heads. It makes for a neater and more secure installation.