i wouldnt add that much weight with the water in the tire, when you can just custom cut some turf tamers and ice screw them to death, and make a decent wheelie bar out of aluminum for it...that will save you 15-20 lbs and probly a couple hundredths off yur e.t., all that water has to create alot of drag on the fornt end when it tries to get rolling too.....i know the cr500 has the power to overcome it, but i personally would find a better way to keep the front end down while putting the weight on the back wheels...
1985 Honda ATC250R drag trike with s/t kit and full drag CR hybrid motor and drag chassis...
1986 Honda ATC250R daily rider fully modded engine, +4 swinger,etc...
1997 Polaris Storm 800 triple, boyesen reeds, dg individual silencers, 240 studs, 123mph on radar...