FWIW I have decided to go with Clarke - cheaper and uses stock shrouds so cheaper still. If my shrouds were all messed up I would go with IMS and Polisport YZ shrouds. I'd be interested in knowing how this works out as far as the fit & finish. I may switch from the IMS to Clarke at some point only because I have perfect stock shrouds and graphics up in the rafters and would kind of like the extra .5 gal capacity. One thing to consider between these two tanks is that the IMS works for both YZ and WR and the Clarke 3.6 only for the WR. I was trying to think why that is and I believe that being that the 3.6 is made for the WR, it likely has a better fit with the WR seat. On the IMS, the WR seat fits fine, but seems like there is extra space as I believe the YZ seat is a bit wider right at the front where it runs up the tank.