You could possibly get away with eating more and gaining less fat with the help of TRex. Isn't Big Blast a MRP? You could use that with any supplement, while bulking or cutting, just as long as your calories are in your target range for your gain/loss goal. I'd only avoid it if you are cutting and you can't get in enough quality food for proper nutrition w/ the inclusion of the MRP, but I doubt that will be the case.