A few months ago, I purchased a larger tank from IMS. It is holds about 3.2 gallons and is good for about 90 miles of fast trail riding. The IMS tank fits my 2001 XC250 very well. The tank has a recess on the bottom to accomodate the rear shock upper mount (which sits above the frame rail). Note: Clarke tanks do not have this recess. I have heard they are modifying their mold to overcome this issue. All screws thread into brass inserts (such as shroud screws, petcock screws, and front mounting bracket screws). The tank comes with a plastic gas cap but you will need to reuse the breather hose off the stock tank. Also, you will need to buy (or reuse) a petcock. The tank is well made and I like the natural/white color to see my fuel easily.
Overall, I have been very pleased with the IMS tank. I really don't notice the size while riding. The tank is wider and taller than stock, since the tank is limited by the frame rails. I don't have a steering damper, so I can't comment on any interference issues.
Here are a few photos to show a comparison between the stock and IMS tanks.
Here is a top view comparison:
Here is a side view comparsion:
Here is another side view comparison:
