Hearing all you guys talking about YZ tank and seat on WRs got me curious to try it. TT member Sylvain had me try his Acerbis YZF tank with YZ seat on his 426. After seeing Sylvain's WR set up with the big Acerbis YZF tank and YZF seat, I have the feeling that the result is a not so flat seat when compared to the stock YZ tank. Anyone else noticed that? Just have a look at the YZF 426 set up on the IMS and notice the "u" shape of the top line of the seat Compare with TT member WR426madness set up with the stock yzf tank. I think the IMS and Acerbis YZF tank don't really offer a significantly better position for the 426s. Maybe you can sit an inch or two closer to the front end...? But probably not much more than that. Look at the WR line. For the 450s, IMS aftermarket tank for YZFS creates a result that is closer to the stock YZF tank. I'm a bit disapointed because I would have like to have the flat feeling of the stock YZF tank but I want to keep a fuel capacity over or at least close to the 3 gallons. I thought IMS or Acerbis YZF tanks could be the way to go but I'm now more than hesitant. I've tried a guts racing tall seat on a WR426 recently. The tank was the stock WR tank. I think the result is at least as good as a Acerbis YZF aftermarket tank as far as riding position. It is so thick that it creates a straight line from the back end to the point the seat ends close to the tank cap. By doing that, you are seated over an inch higher from the pegs which is also great when you are at 6'1'' It is also darn comfortable... Not too soft, not too hard, great shape. Well this was just my humble opinion. I havent made a lot of track yet so my opinion might change but for now I think I'll stick with the original tank and buy one of those guts. If I had a WR450, the story would have probably been different. IMS YZFs tanks offer good ergos and bigger fuel capacity (3.1 gal) over the stock WR450f tank (2.6 gallon in 2003 and 2004 and 2.1 gal in 2005). I think it is a no brainer.