Hey Rob. I got the Yamaha A-arm plates and the differential plate for the my daughters 350. Still haven't gotten it out on the trails yet, so no operational feedback for you. I will say they seem to be well made and easy to install....I had my daughter install them (with me supervising). As for the belly plate, the stock plate is plastic but of a pretty good thickness, so I decided that I would go with it and see how it did before going to the expense of getting the Yamaha belly plate. The stock plates should be okay since my kids mainly ride trails and don't get into many rocks. I did run across a post on this forum about various after market plates along with their prices...I'll try to find it again and let you know.
I will send pics after the first camping trip.