Buffy,

Shorter leaders are fine with sinking lines. If you use a long leader with a sinking line, the fly tends to float above the fly line. With a shorter leader, the fly tends to sink at the same rate as the fly line. In one of Lefty Krey's books, he has a picture of a 6" (yes, inch, not feet) leader with a sinking line! I think that's an extreme example, but you get the picture.

Good luck. Like you said, you now have an excuse to buy more tackle!