@deranged_midget: Isn't base form GT Goku supposedly strong enough to handle Kid buu without any transformation? SSJ1 transformation would make him ludicrously strong let alone SSJ4.
Honestly, I don't know. But End of Z Goku did go up against Uub, who was the opposite of Kid Buu as he was gaining and learning his powers. He fought with him in his base form and then later on to train in the Hyperbolic time chamber.