And if you loose one in flight, you will have a hard to control tail heavy plane. Personally, i like my weight attached to the plane and not spinning in front of the engine.

The extra weight on the engine also acts like a fly wheel, it can help smooth out the engine vibrations, but it eat a little power and also causes the engine to be slower to respond to throttle changes. some of those characteristics can be good, and some can be bad.

You have to decide if they are good or bad for your circumstances.