And yes Magic card shims. (I sell about 10K a month worth of them so its something that's always laying around). I've also used manila envelopes cut up with good results.
Interestingly enough the first ones I built up using manila envelope pieces. The next time I reconed I used Magic cards and gained .2db (though I think it was more likely due to using lighter cones LOL).
**** rain all day, don't like to take the TL or laptop outside in the rain.