I'll go on record to say that you do not need a 3 axis gyro. Earlier this year I went through the same delema and received a lot of mixed replies. I have successfully installed a 5 blade head on my EXI 450 with a MD500 fuse and it flies great. The big issue is setting up the head correctly. I found a really useful setup tutorial that I will have to look around and get for you that covers the setup very well. My setup was from Copter X and is just the 5 blade head and a set of plastic scale blades (both from CoperX). I'll attach some pics.
-Jesse