Personally if the plane is goin to be sitting for anything more than a week I would chock all three wheels and leave the parking brake off. It will stop you getting problems with the brake pads binding to the disks. As well you can get areas of rust forming on the exposed bits of the disk and none under where the pads are giving you differences which will cause judder and possibly warping. This is but a theory so good be bollocks. Hopefully A and C will be along to correct me if i am wrong.