after the first 60' its nothing but dead weight. I think you'd be better off tunning the suspension (lowering) strapping or whatever... And keep your weight over the front end as much as possible. I get as far up as possible and lay on the gas tank.
Not sure if this applies to bike, but from my experiance drag racing cars and setting then up for drag racing, for every 100lbs of sprung weight removed from the vehicle you shold expect the ET to improve by one tenth (given that no power was added and the conditions are exactly the same as they were on the previouse run). Also most drag racers will tell you that for every tenth picked up in the first 60' you improve by two tenth in total ET. So if the weight you propose to add, drops your 60' by more than .2 then it may be worth it in total ET, so long as it doesnt effect the aerodynamic performance of the bike, and doesnt block your radiator (you really dont want to do that either). However you keep in mind you probably wont pick up the full .4 on ET if you drop your 60' by .2 because you added weight to the bike and changed nothing else