Anybody make such an animal? Any other tips for mounting a wireless receiver (AT1800) on an XL2 would be appreciated.

B&H Sells the BEC Mounting Box for the 1800 Series (AT-1820 for the Dual Version or AT-1810 for the single version) as well as the BEC Vertical or Horizontal Shoe Mount adapter.

With the BEC Box you can also mount the 1800 on the back of the camera battery without using the shoe.

http://www.bhphotovideo.com/3results/controller/home?O=search&A=search&Q=&shs=at-1820&ci=0&sb=ps&sq=desc&atl=%7EBrand_BEC

http://www.bhphotovideo.com/c/product/463339-REG/BEC_HSAVERT_BEC_HSAVERT_Vertical_Shoe.html

http://www.bhphotovideo.com/c/product/463337-REG/BEC_HSAHORZ_BEC_HSAHORZ_Horizontal_Shoe.html

Perfect, but dang! I've got heartburn on the price! Will that box mount to the accessory bracket at the back of an XL2?

Yes you can.

I should have made it clearer when I wrote:
"With the BEC Box you can also mount the 1800 on the back of the camera battery without using the shoe"

Thanks much.

the dual 1800 also comes with a canvas holder witth a nice metal clip that can fit on some battery brackets.

Regards,

Ty Ford