The RevMax is a great limiter and will definitely help with your over speeding condition. A governor is worth the money and you will notice a big improvement in consist ant head speed.
If you want an extremely versatile and easy to setup governor, check out
http://www.aerospire.com/index.html. The MultiGov allows you to set the gov for different head speeds in all three modes and the biggest feature is, you punch in the head speed you want and that's it. No more tachs. You can also use it as a governor or limiter in each flight mode separately.