I rewrote the script that I blogged about over the weekend to convert shorten files to WMA 9 lossless format. You've got to have the shorten utility on the path and have Windows Media 9 Encoder installed.
Download the SHN2WMA script.
BTW, I claimed that the WMA lossless format was half the size of shorten's format. Turns out that the ratio varies widely. For the concerts I've converted, I've seen as reduction percentage between WMA and shorten be as high as 55% and as low as 12%.