Who does not use heat shrink tubing in the shack? I've settled mostly on 3:1. Sure, if I want a really tight fit, or if I have too much room to spare, I'll go with 4:1, but 3:1 is my standard. Here are a few options, two of which I have purchased and used myself. Frankly, with the number of reviews for each of these, I'm fairly confident any of them will do the trick.