Go2Tex, what I do is place the tip of my thumb right up against the roo hide as it enters the cutter. By adjusting the pressure on the roo as it enters, you can keep it from curling up. Basically what you're doing with your thumb, is what you suggest with the plug, but you don't have to figure out what size of what to plug in there.
Also, a VERY sharp blade really is the key.
Ken