I own a 2004 WR450 and need the bigger fuel tank for long rides down Baja. I have looked at IMS , Acerbis , Zipty, and Clark. I get different answers from shops and manufactureers. When I put the bigger tank on I know I need YZ450 radiator shrouds. Do I need a YZ seat also? I have been told yes by IMS, but No from a couple local shops that sell the stuff. They say the WR seat is too wide and doesn't work. I really dont want to purchase a tank and shrouds then lead into a bunch more costs (seat is $150 from Yamaha ). Anybody out there running the Acerbis on 2004 WR450? or an IMS on 2004? How did they fit? What do you recommend?