SBC CON FE slipping, need advice

[FordCummins]

Im running SBC's CON FE clutch in my truck, and have put roughly 2000 miles on it since installing it. Under heavy throttle, in 5th, sometimes 4th gears it will slip. I make sure the clutch is fully engaged before I lay into the throttle, and it will sometimes slip, other times not, using similar conditions such as (speed, throttle input, load). I wont get a chance to pull the truck apart for at least a month to replace the disc (if thats what it needs). Woody at SBC told me to give it 1000 miles of around town driving to let the clutch break in. I definitely have this many miles, and am still having slip issues. I havent contacted SBC yet because I wont be able to pull the truck apart for a while, and want to talk to them once it is apart. Any suggestions on what problems might be causing this? Im sure that Im not even close to the power limit this clutch is good for, based on the mods listed in my sig. Thanks for the help guys.