The longer teh stud, the easier it will snap. You can try the simple physics with a pencil, take a full length one and a half, see which one takes less preassure to snap. If you're going with a 3/4" just go woth the fill 1" since the 1/4" will make almost no difference at all. If you're running around drag racing, wider tires will get you more of the handling characteristics you're looking for than spacers will.