I just went through this learning process (with the help of some advice from the YYE help desk and from LarryG.), and here’s what I learned–
Most people find the response on the Juggernaut, as delivered, just way too slippy. (Some say the problem is only when you’re using polyester strings, and that the Dif pads work OK with cotton, but it’s so bad that I’m skeptical of this.) You’ll notice a big improvement if you switch to a softer, silicone-based pad. (The Dif pads that it comes with are hard rubber-based.) The size you’re looking for is a pretty standard “large bearing broad pad.” So pick up something like Crucial’s Ghost pads (now called “Yath pads” at YYE) or Duncan’s large bearing Silicone Stickers. (NOT Duncan SG stickers, they’re “slim” size.) I’m using the Ghost and am pretty happy.
However the Ghost pads sit pretty low in the deep Jugg response grooves, and so maybe you’ll also want to use a slightly thicker string (or at least not a thin one). I happen to be using what sniffy recommended – Toxic Dragon strings because, to me at least, they’re slightly thicker than average. In any event they work pretty well in conjunction with the Ghost pads. The thick version of Kitty strings would probably work too.