Hi Boobala,
If you are talking about mounts for a car versus an airplaine, they are two totally different things. I do make aircraft parts for Boeing and Bombardier, and the procedure to go through making a part is much more intense in papertrails (you know what I'm talking about) and making the part is again another thing. You have to find the right grain structure of the material for the best stress resistance and all radiuses must be put on in all corners and the part must go through a few stages of stress relief and shot penetration to release any levels of stress, and then go through x-rays or ultrasound in order to pass inpsection for an airplane. Now if you want all those levels to be done for a car, it could be done, but the price of the mounts would be over $1000 easily.
But like you said, the rubber insulators will reduce most of the vibration of the motor already, so the corners will be okay. You are also right, ideally everything should be radiused, which I could do right now, and the center section will be thinner. Next time, I'll put a small radius in there to satisfy my toughest critics
I'll try to post some more pics from other angles of the mounts soon.
Rick