Joe,

Sorry for the delay, but I had forgotten to take my camera home the other night, and I was out of the office snowboarding most of the day on Thursday (I know, I know..I lead such a hard life).

Anyway, took some pictures of the Thule cargo box last night (see below, and excuse the crummy VX in the background), and after a quick search of Thule's website it doesn't look like they make the Cascade XT anymore. It also looks like they have revised their mounting clamps. As you can see in the picture, my box has big metal u-bolts that feed up through holes in the bottom of the box into a clamping mechanism inside the box. The u-bolt and the clamping mechanism can slide back and forth in the slots that you can see in the pictures. I couldn't find any information on Thule's new mounting hardware, but I can only assume that it still slides back and forth some to accommodate different roof rack systems. You might be able to find an older version on Ebay.

Hope this helps.